Funny, I just read this post over on CC that epitomizes what *can* happen on a cruise line that expects tipping. Here's the relevant part:

" have never been so appalled at the service anywhere. For those people who ordered from the bar, a 15% gratuity was automatically added--fine. But, these servers held their hands out for more tips after delivering the drinks! On the day of departure, the cabin steward rolled up the tabs of those who had left him a gratuity, and placed them in the door handle, and slid the others under the door--letting him know exactly who had done what. If you did not leave him a tip that he liked, he went after you and demanded his tip. Excuse me?????? We actually heard him say "I want my gratuity" to one family. They obviously did not think that he deserved one and did not leave one, but they should not have been hunted down and talked to like that. How rude. "

This was on an RCI ship. Anyway, there is so much controversy about tipping on cruises -- I've read so many varying opinions and experiences. I personally commend RSSC for their tips-included policy, as I think it's the best of both worlds. The crew doesn't expect tips, so there isn't any incentive to provide varying degrees of service (there seem to be many on CC that believe that the crew treats passengers differently based on pre-tipping, or what they expect to get, etc.) Those that wish to tip may do so in a variety of ways, and those who don't aren't penalized or made to feel bad for not doing so.

I don't really know how tipping impacts the behavior of a crew -- I'll leave that question to the sociologists and psychologists. But I do know that I am truly looking forward cruising where I don't have to think about it! :)