Maybe not outright avoid, but to me tap water is kind of a litmus test for how a restaurant is going to treat me. If I feel like I'm being fleeced before I've even gotten around to ordering, I don't feel comfortable. I like feeling comfortable when I sit down to eat, be it at home, at friends', or out. Incidentally, that feeling also tends to be what keeps me at the table (and ordering another round of drinks, dessert)...everybody's happy.