It is not necessary to overclock any component. People usually do it just for the kicks or to get some more performance out of their system. In this case I think you should overclock only if you want to have some fun since that CPU is powerful enough for today's games
^Exactly. Just because you can, easily, does not mean you have to. I did because my CPU would be a "little" slow in some things otherwise. if your system is fast enough to play all your games and run all your applications to your satisfaction, the only thing overclocking will do is use more power.
I'd like to make mention of something very important with modern CPU's. Simple clock speeds aren't what makes modern CPUs 'powerful' when compared to other processors, especially when comparing to older gen CPUs. For each clock cycle, new CPUs (in this case, an i7 3930k) are much more powerful and capable of processing more per cycle than a CPU at the same speed 3-5 years ago.
The only benefit you'll see in overclocking an i7 CPU is an improvement in benchmark scores...that's about it. If you are looking for better gaming performance, overclock your video cards or upgrade them.
Too much logic in here, time for some irrationality!
If I had a 3930k, you can bet I'd be making that chip beg for mercy. They overclock quite well, and as you can see from my sig, I like to push my hardware to (and past) its limit.
I find the process of tweaking the hardware to get more performance to be a lot of fun, and who knows, maybe you will too. You certainly won't get any additional gaming performance out of overclocking it, but with a decent cooler you should be able to hit 4.5 GHz without too much trouble.