Here, here. All good points Doug.
Also, this dovetails into another discussion on this board a few months ago concerning tipping -- and this is from a different perspective.
Sometimes, you can have one guest who is a problem for the other guests. Either they can abuse another's personal space or cause a problem in the diving itself. Since most liveaboards are setup with the idea that you need to tip at the end of the week, the divemasters are very reluctant to do anything about these problems. Same with destroying the reef. They don't want to upset a customer. They will give lip service to the folks that complain and try to mollify them as much as possible while still not saying anything to the bad actor causing the problem. This is because they live for those tips and they try to make everyone happy to maximize their income. I don't personally blame them for this stance.
However -- not dealing with one bad actor on your boat may cause 3 or 4 people not to use you again. The boat owners need to know this. The best policy would be for the liveaboards to charge a complete fee and make it clear the tip is included. If one customer is causing a problem, *deal* with it. I personally have been on a trip recently where one guy was crashing into me constantly and when I mentioned it to the the divemaster he told me the other guy was a paying customer too and he couldn't do anything about it. He suggested I talk to the other diver about the problem. I "talked" to him about it in a very loud voice to ensure I was understood. But still. I paid a lot of money to go to the far ends of the earth and I shouldn't have to deal with that crap.