I think a lot of people when they go to the Dominican Republic feel tied to their hotel - probably because it's all-inclusive and they are reluctant to go out and pay for food and drink elsewhere. But that's not such a bad thing. I've been to the Dominican Republic three times now (1999, 2000 and 2001) and have stayed in Puerto Plata twice and Bahia Maimon once. The choice of activities on offer in the Dominican Republic as a whole are very limited!
Even when we were there, the hotel was "popular" (but not "taken over") by the local people. At the end of the day, the locals are taking a holiday, just like you and everybody else.