I disagree. I have a 22" CRT monitor with an A/B button on the front. It has two VGA connections on the back allowing you to hook up two different computers to the one monitor. I'm pretty sure most LCDs these days will allow you to switch between the VGA and DVI inputs as well.
I do agree that if you want to use two computers (or more) at one station, get a KVM. Pretty cheap these days and easier then moving keyboards around.