I get bugged when someone doesn't pay their fair share. There have been numerous times when I have had to overpay.
If I'm going out with a group of people, I make sure to bring smaller bills, so I can pay my fair share. I don't just bring twenties and ask if anyone has change. What I order is based upon how much I have to spend (factoring a 15-20% tip). I wouldn't think it fair if someone had to pay extra because I indulged myself, and I don't think that I should have to pay for someone else's high time.
I just think it's the considerate thing to do.
I have a friend who always asks for seperate checks (even when the group is pretty large). I think that's pretty cheap, but if that's what he needs than that's cool with me.
I also agree with JS - Fake people suck!