Here's a MeFi thread about tipping in restaurants, specifally about the practice some restaurants have of imposing a mandatory gratuity on large parties.
In my own experience, I hated the fact that first, my restaurants didn't have such a policy, and that second, when the company finally decided to put such a policy right on the menu, our district manager (who had the brains of a flea) refused to allow us to enforce it.
The simple fact is this: while most people who tip in small parties assume that large parties result in larger tips for the server, this simply is not borne out by my experience. It was the rule, rather than the exception, for large parties to undertip, often less than ten percent of the final bill. I once had a server knock herself out waiting on a children's birthday party that was in the restaurant for two hours, during which she played games with the kids, kept the drinks full, served the food and the cake, and took no other tables in the process. Total bill: $120.00. These folks left her two dollars.
Yes, that's an extreme case, certainly the worst one I ever saw, but the fact remains that my servers made less money for waiting on large tables, and that it was this way in both restaurants I managed. Additionally, large parties tend to remain in the restaurant much longer than smaller ones, which gives the server a double-whammy because now his or her section isn't turning over as quickly. Someone in the thread says that a party of eight can't take any longer than two parties of four, but this is false, because there's a special dynamic that exists with a party of eight. In almost all cases, a party of eight involves people meeting at a restaurant for some manner of special occasion, which is rarely true of smaller parties. Ergo, these larger parties always take longer in the restaurant. (The only exceptions were large parties that would come in after the dinner hour for dessert and coffee, and even these could be there quite a while.)
Somewhere along the line in the MeFi thread, by the way, someone makes the point that there are other minimum wage jobs out there, so no one has to wait tables. This is nonsense. The fact is that in a well-run restaurant with good servers, the wait staff make significantly more than the minimum wage. In fact, there were servers at the family restaurant where I worked who, because they were very good and therefore worked on each of our very busiest meal periods, actually made more than I did, as a salaried manager. People don't wait tables because the restaurant was fully-staffed on bus-boys; people wait tables because it is good money, and the hours are conducive to doing other things with one's life (such as going to school, writing novels, auditioning for shows, et cetera).
I do think that tipping, as it has evolved in the United States, is a damned goofy system. But I also think that there is nothing I can do to change that system that doesn't involve stiffing servers in the process, and I have worked with too many servers who were good people with kids and families and worries of their own to do this. Yeah, the system sucks, but it's a system that affects real live people, and in my mind, the needs of people tend to outweigh my desire to buck a system.
UPDATE: More here.