A lot of interesting, different perspectives here.

I have worked as a waiter a couple of times. The last time, I was trained well and expected to perform well. I did. As a result, I earned excellent tips. I made more as a waiter than I had as a salaried state employee (the job I lost prior to becoming a waiter). My wage as a waiter was $2.35/hour plus tips.

As others have mentioned, I did not expect much (if any) tip if I didn't perform my job well. Because I worked hard and made people genuinely happy, they paid me well. That's the way it should work. My point? If someone deserves it, tip 'em well! If not, don't feel guilty about not tipping them.

A short aside-- I live in Japan, where tips are not expected and often returned/refused. I still tip people if they help me out or do a particularly good job. This includes restaurants, hotels and taxis. Folks usually try to refuse the tips, but I insist. They are invariably pleasantly surprised.

FWIW.

Kento