When (rarely) in the US, I abide by the when in Rome... philosophy and tip for service at the appropriate level. I would rather pay a higher overall cost for food and have my waiter earn a liveable basic wage and then be able to express my pleasure in exceptional service with a tip but it's not my country and I dont make the rules (plus, I'm sure no one really cares what I think ).

What does really irritate me is something which has been touched on in the last couple of pages. I abide by the culture of the country I'm visiting, by tipping at the appropriate level and in the appropriate circumstances. I live in a country where tipping is not expected (although I guess it would be standard to round up a bill if it was fairly close), and strongly believe tourists should abide by those cultural norms and not tip as standard (and certainly not at 20%). I do tip for exceptional service and think it's fine for people to do the same, for the record.