Do you still tip your restaurant server even if the service was atrocious? [View all]

If you're dining out at a sit-down restaurant where you are given a menu at your seat and the server takes your order but the service during meal is atrocious, do you still leave your normal tip for the server? I'm not talking about a place where you stand in line to order and then take a seat to eat. I'm talking about your standard, full-service restaurant and truly awful table service - not something minor (like delivering a regular soda if you asked for diet) or something out of the server's control (like food quality).

I suspect most DUers will give the server the benefit of a doubt and still leave a tip. I'm just not sure how high that percentage is. Also, is there a point where the service is so bad that you would not leave a tip?