Kind of harsh, don't you think? Many waitstaff are paid sub-minimum wage in the expectation that their tips will make up the difference. If I remember correctly, in Ohio the minimum wage for tipped employees is less than 50% of the rate for non-tipped employees. Additionally, most wait staff have a % of sales assumed as tips and reported to the IRS. Which means they have to pay based on tips that they may not even receive. Admittedly, this is not a normal occurrence, and most decent waitstaff will make more in tips then gets declared, but it's something to think about.
In a (chain) restaurant, the servers may have to tip out the kitchen, bussers, and hosts. it can eat into those tips real quick.
I start at ~20% and will go up 10 or down to 0 depending on the service. I have been there before, and it takes a certain kind of personality to put up with the public.
There have been a number of threads about visits to brewpubs, etc... where the waitstaff was pretty clueless and couldn't explain the food/brew. I can't remember seeing one about someone going in and having a great experience because the server could speak intelligently about the beers and food. It's a rough situation where perfection is the expectation, and the only reward comes from being "better than perfect".
<climbing down off my soapbox>