I don't have a desktop PC at the moment but I put my laptop to sleep every night and unplug it from the wall (as well as the charger from the wall.) I turn it off maybe one or two times a week just to clear up anything but not very often. I can't see a reason for not putting the computer to sleep or standby, it just doesn't make sense not to.

Most time time my PC is on because I use Windows Media Center. But when I'm done watching TV at night I sometimes put it in sleep mode. It's setup to wakeup when it needs to record.

I hate to break it to people here but mechanical wear and tear is negligible unless you're turning the system on/off every few minutes. Maybe a cheap motherboard fails with less stress but from the articles I've seen here motherboard manufacturers take stress and fatigue into consideration when testing.

put my computer to sleep every time I step away from it more than 10, 15 minutes; The laptop stays on from the time I come home to the time I go to sleep because I have the Skype on, and because of Skype I'm looking forward for something small between 7"-10"-12" with web cam to take less power

Most of the times I leave it on, unless my computer is doing absolutely nothing. It's also in the room I sleep in so sometimes i don't want to hear the sound of the fans spinning.

I always turn my PC off unless I'm downloading/uploading something HUGE or running a virus scan (not that I ever get viruses, just for peace of mind)

My computer is a heater in the winter months :-), but it gets unplugged from the network when not using the connection for anything.

Folding @ home 24/7
thus my system is on 24/7 (most of the time..)
1.5kVA UPS makes it easier to keep the system on while I am not around.

To that I will add that I've never had a 24/7-on hard drive fail on me. I have, however, encountered the dreaded clank of death in many mainstream-use hard drives.

I've had yet have a hardware that can't last me 8 years and I shut off my systems daily. So to me, leaving the PC is better is a myth and is costing me way too much money than to shut it off. Heck, even if I do leave it on, the cost will be greater to run the systems than to buy a replacement.

Thus, the "advantages" of turning your PC on constantly has been nullified. Plus, for most PC enthusiasts, they replace their core parts or build an entirely new machine every 2 or 3 years. So, if wear and tear is an issue for them leaving them to turn on the machine, they'll never see the "wear and tear" since they're going to replace it well before their deaths.

So instead of hurting the environment and your pocket books, turn off your systems at night or if you're not using it for more than 3 hours. Even if you have to leave it on, at least let it do something than sit there idling.

Always leave everything on.

i leave it on 24/7. i have an old crt monitor that is on it's last leg and if it turns off i need to hit it with a pipe so that it works again. no joke.

My habit is to put my computer/laptop in sleep mode, which gives me full access within seconds of hitting a key. This is primarily to stop the fans from spinning, because otherwise they amass a ridiculous amount of dust, and its a pain to clean every week. Also generates noise, heat, racks up electricity costs.

I'm somewhat concerned with hard disk integrity, seeing as I've had a logic board go up in smoke, and a couple disks become corrupted. However, I'm also convinced that the nature of a spin up/down cycle isn't going to do anything to a HDD (you don't keep your car's engine running overnight, do you? ok bad example....kind of). I put my faith in the engineers of WD, Seagate, Hitachi...etc to design their spindles with an infinite fatigue cycle life.

still not happy with mechanical components? time to go solid state.

nope
its all about consumption

well since bit torrent is throttled heavily by bell canada i HAVE to leave it on if i ever want to get anything downloaded. not that i'm downloading massive torrents everyday. buts its just that i get such horrible speeds, the same torrent i started to download last month is still going. and like others here have said: to leave it running a virus scan every once in a while. but to be honest the fan noise doesn't bother me and since i use it a good portion of the night sometimes i just fall sleep without turning it off. and it really doesn't impact the power bill either.

nope! i dont shutdown my comp. i use speedfan which turns down all my fans super quiet so i can sleep at night with my computer in my room without having to listen to a vacuum cleaner xD

No. I know the Earth is warming but there is also a lot of natural heating going on. Did you know there was a mini ice age during the late 1800's and early 1900's? If we were around during the mega ice age and everyone was leaving there freezer and fridge doors open for 5 minutes a day we would be viewed as the cause of it. Grant it we aren't helping we are the %100 cause of it. I turn off my LCD at nights just because it comes out to be 5 bucks a month cheaper on my electric bill when I do so, (I have eight LCD's not including HDTV's.) But I also completely unplug them instead of just turning them off since they are all at chest level and easily unplugged. In addition all my motherboards are ASUS and take advantage of the EPU that comes with the ASUS boards. I'm doing my part in a small way but it's because it saves me a little money.

yes

I leave my pc's on 24/7. The power a pc uses when not doing anything is negligble. And yes I do pay for my own electricity. My bill is around $50 a month if my pc's stay on or off. I run 3 desktops and 1 laptop

I absolutely turn off my computer, my printer and my monitor when I am not using it. It sure cuts down on the electricity used. I backup daily. If a hard drive breaks, which has never happened in the 15 years of computing, then I have another hard drive loaded with the OS, apps and drivers for the PC. All I have to do is connect it and transfer My Documents to it.

Those that do turn there PC off at night, should also disconnect from the outlet or turn of the PSU or the Power Bar. If the computer is off, and the PSU is connected there a Standby circuit that remains on. This standby circuit warms up, and can get quit hot in warm climates since the fan isn't running. This can, on rare occasions contribute to PSU failure. Just a for warning.

As for me i leave my PC on all the time. Although i have been thinking about trying the Sleep Mode after a few min of no use. Not sure how Win 7 handles it.

Yes and the reason i don't leave my big PC on is because I run a quad core, 4x2 gig of ram and each one takes some power, 2 HDD a 22" monitor , 2 fans, video card fan, and if you add up all of then you will see that takes some power; now there is a big difference between this and my laptop and for me each watt maters + I don't like to be connected 24/7 to the internet

I turn it off when i'm done but i'm usually always doing something on 1 of my computers but usually every other night all the computers get a rest or so.

I never shut my computer off unless I am leaving town for an extended time. I like having instant access to my system. In addition, I use a low power system for most uses, and turn off the monitor when I leave for more than a short while.

1000 watt power supply on the new rig and the most recent electric bill means it's getting turned off. got a lot of other devices in varying states, but unless there's a torrent going, or a RAID reconciliation, it's getting shit down.

has folding @ home helped to find a cure for anything? provided a new insight? because as far as i know this is a waste of energy

I've never had a hard drive (or any other component) die out on me because of turning the PC off each night. That said, both my wife and I have 750-watt power supplies, my daughters' PC runs a 400-watt supply. To leave all of these on--even in hiberation--would really eat into the family budget over the course of a month.

It's not about being green, as not paying money to the local electric company. Besides, seeing as we're all away at work (or school) for 10 hours each day, plus sleeping for another 6-7 hours, there really isn't THAT much time we spend on the home PC's (though not for lack of trying...).

No I leave them on. 25 years of this and the ones left on always last longer. Thermal expansion/compression.

Uh.... sometimes I turn off my laptop but it tends to stay on longer than I would like. I try to turn it on standby but forget half the time. I tend to be high a lot and with people and well it just slips my mind and I just fall asleep.

My desktop is just busy downloading torrents I've had it less than 2 months its run time is over 47 days.