Have You Ever Not Tipped A Waiter? When is it Okay Not to Tip [POLL]

Tipping is always an interesting topic to hear people discuss. Some people say you should always tip 20%, while other people say 15-18% is just fine. But what happens if you have terrible service somewhere? This story brings up the question, is it ever okay not to tip? From KFYO.com:

In Houston, Jasmine Marks went out to eat with her family, and was met with sub-standard service from the wait staff. The restaurant then added an automatic 17% gratuity to the bill, because there were more than 5 people. The guests refused to pay the gratuity, so the restaurant refused to let them leave.

So what do you do when you get bad service? Have you ever refused to leave a tip? How bad does the service have to be? Let us know your thoughts in today's poll.