You can add oysters to the list of ocean dwellers that humans are wiping out by way of our stomachs and unwillingness to preserve their habitats. The good news is that not only is oyster farming sustainable, it is actually good for the environment.
This is a good time to mention the Monterrey Bay Aquarium guide to eating seafood. I use the iPhone version. Having reviewed the whole thing, here’s the basic upshot. If you stick with fish or shellfish farmed in the United States, you’re probably in the clear. Most wild seafood and nearly all seafood farmed overseas, especially in Asia, is a bad choice. Oh, and if you still eat bluefin tuna (also known as the stuff they make sushi out of), you are part of the problem.