I think tipping has evolved from "a little extra" for exceptional service to a living wage in some industries, especially restaurants. It's gone a bit too far in the U.S.... waiters/waitresses shouldn't have to depend on the whims of customers to determine if they can pay the bills - they should be paid decently. At the same time, a customer eating in a restaurant should enjoy a decent level of service, regardless of tipping.

While on the subject of tipping, getting room service at a hotel is outrageous. Besides the item cost, you are often charged delivery and an 18% tip, plus there is usually a line for "additional" tips on top of that....

And to answer the original poster's question, I tip waiters generously (knowing the above, I sort of have to), but don't tip counter folks or leave money in tip jars. How else am I to get the food besides them handing it to me?