My friends and I do a ski trip every year. There are 12 of us. There was a travelzoo 2 for 1 coupon for a fancy restaurant in Vail. Before buying the coupons, I called the restaurant and asked them if 12 of us could use the coupons on a Tuesday night during a non-holiday week. The restaurant manager said of course and said he was happy to have us. We spent about 1 1/4 hours in the bar prior to dinner. We had a great bartender and paid our hefty tab with a generous tip to the bartender who took great care of us.
We were seated for dinner. When the waiter came, I told him we had the travelzoo coupons and gave him the name of the manager who okayed everything. The first thing out of his mouth was, "I hope you realize you are supposed to tip on the full value of the meal." I was so stunned, I did not reply. The restaurant was half empty. Our service was terrible and every time he had an opportunity to remind us of the tipping expectations, he did.
My group is a group of professionals. While we are all happy to find a bargain, we are not cheap when it comes to tipping. However, his attitude made me want to tip him 0. I called the restaurant afterwards and received a huge apology and an invite to a free dinner. The whole thing left a bad taste. The waiter would have been much smarter to give us great service and he would have been rewarded. Asking for a tip or assuming your guests don't know about tipping is condescending and rude.
I've seen that if you're so disgusted with the service that you should tip $0.01 (one penny) as that shows you didn't forget to tip.
I've had some pretty bad restaurant service over the years where I've considered the $0.01 tip option, but I've never done it... The above experience would have put me "over the edge" as it were though.