From my experiences on the eating side, I'm not surprised that business meetings tend to be large tippers. Everyone is (usually) having a good time on the company dime and the tip is other people's money anyway. The problem with a group of individuals--specifically where everyone is paying for themselves--is that some people often don't end up chipping in enough and after a couple rounds of "we're a bit short here" the waiter ends up eating the shortage.

Even if it doesn't happen a lot, the effect on the waiter who makes 5% off the group of 25 they've been serving all night can be considerable.