I have worked in the service industry and I agree with tipping to an extent. Bellhops (who deliver to the room/car), bartenders ($1 avg per beer - more if the he/she gives buybacks from the bar), waitresses and busboys (for meticulous service) always get tipped well.

However, I am still up in the air about tipping hotel maids. Here in the U.S., maids in most hotel chains are unionized workers so they are paid decent wages and benefits. Those that aren't unionized (Marriott is one, I believe) are paid comparable wages. Am I required to tip them anyway? I don't leave my room a mess so there is actually very little to do. Is this expected in major hotels in metropolitan cities outside the U.S.?