Should one give tips if the service in a restaurant is bad?

First off you don't have to leave a tip, but you always should. A server is paid less than half of minimum wage in the U.S., in states that allow it. The tip is a way the government allowed restaurant owners to charge less, and still make enough profit to stay open. Without the tip you would pay an extra 10% for your meal at a sit down restaurant. So I would encourage at least the 10%.
Second, many times the reason for bad service is not the servers fault. The restaurant allocates a certain number of spots in it's schedule for each day and time period based on past history. They may have been an unforseen circumstance that caused the problems. It could come from the kitchen being behind, from the dishwashers not able to keep up on clean dishes. Again that might not be the book's or dishwasher's fault, like I said it just could be too busy for the staffing allocated.
Third, another problem at restaurants is certain customers feeling of entitlement. These are not slaves, these are not servants. You should expect good service, but not to the point of thinking you are the only one there. I am not saying you fit that description, but one table being that way can disrupt the whole evening for the server.
Fourth, the server may be having an off night. They may be having problems outside the restaurant that in a perfect world they wouldn't bring to work, but you try that at your job, when you just had a fight, or you just got off the phone with a bill collector, or a child is sick, or a parent has berated you. It's easy to see how their mind wanders.

15% is the standard tip. 18% is a good tip. 20% is an excellent tip. In reverse, 12% is a bad tip, and 10% is barely serviceable. No tip is not wrong, but not right. The tip percentages are both a guide depending on the "perceived" quality of service and an indictment against the regularly bad tipper in my opinion. I usually try to give the 18%, as having worked the food business I see how much the servers do behind the scenes usually with a smile on their face.

I normally leave a ten percent tip for bad service unless someone truly pisses me off. That doesn't happen hardly ever and I can only think of one instance where I have left less than ten percent.

I was with my grandfather at the time and it was a Friday night in this little Podunk town of probably 1500 (the food and desserts are wonderful) and there was literally one other table that was occupied in the entire restaurant. Two servers to serve two tables. Should be pretty good service, right? Wrong. We were only able to order our drinks, get them once, and place our food order. Our food never came and even though I called the waitress over to our table to ask about our food twice (it doesn't take twenty-six minutes to prepare two chopped steaks) and was never given an answer about the remaining amount of time on it, as she would just say "soon" and go back to the other table to talk to the patrons there as she had been doing since we arrived. After a full thirty-two minutes I wandered up to the counter and got the manager. Once I explained that it had been now over thirty-two minutes and we had only gotten our drinks, we were comped the meal (a whole ten dollars), given a free slice of pie (that made up for it right there), and half off the next time we came in. After finally finishing our meal, the waitress came over and tried to hand us a bill that wasn't even correct and actually asked about getting a tip.

I handed that loser waitress a penny and told her that she has a long way to go if she wants more than that. Absolutely the worst service I have ever had.

Why is putting ketchup on a hot dog or steak sauce on a steak considered a culinary faux pas?

Personal opinion here: ketchup on a hot dog is pretty acceptable. I think 99% of the time, it's the normal thing to do. The only exception I can think is if it's a gourmet hot dog with gourmet toppings where the flavors would clash with ketchup.Steak sauce on a steak implies the steak was a cheap cut or

Why is food so expensive in Detroit?

How it compares depends on where else you have bought food and where in Detroit you are buying food.Detroit city proper has virtually no grocery stores. We have speciality food stores, Eastern Market and Whole Foods. The Whole Foods has lower prices than other Whole Foods (like the one near my house) and more fresh prepared

How come the cooking staff from Noma restaurant don't wear any headwear? Isn't that unhygienic?

Despite what you've seen on Food Network, the kitchen crew at most reputable restaurants doesn't wear any "headgear". They're expected to come to work every day with their hair neatly cut and under control. They're professionals and they know how to keep your food hygienic.Cooks don't actually wear a gigantic, floppy baker's hat like Monica from Friends. They also