In the UK the display of captive dolphins and whales was banned in the 90's.
I agree that habituated marine animals would suffer if the feeding stopped. I wish the tour guides would use the interaction as an opportunity to educate more, rather than just a form of entertainment and a way to get tips. I also wish that the tourists were better supervised.
If it were clearly explained to tourists that the area has been a feeding site by fishermen for years and that this is a highly unusual situation, which enables the lucky few to have these interactions and that this sort of thing, in any other circumstance would be wholly unacceptable, it would be a very useful educational experience for people.
Tourists should be briefed on what is acceptable in respect to interactions with the marine life and guides should set a good example. Unfortunately, on my many trips to Hol Chan/Shark Ray Alley, with 'reputable' guide companies, I've had none of this. Just a 'look at the sharks, jump on in!' and then the showing off stuff with the marine life, which certainly does us no good in terms of our reputation as an eco destination.
I think others have mentioned the illegal harvesting of conch and lobsters by some guides too.