Why would you need a forum on clams? There are only a few different types of claims, a number of different types of disease/parasite problems, and the standard requirements. The biggest thing would be pictures, as that's where you're going to get most of your posts, especially with the wide variety of colors and pattern, not to mention some very large ones that people have grown out.
I think for most people a clam is just an add on to your tank, something nice to have but not everyone has one. They also aren't always available, but when do they come around that's when you get most of your questions about clams.