Of course anyone can form any exchange group they can find anyone else interested in: join a big one, join a small one, join one that is color only, join one that is street photography, one that is traditional darkroom, digital, IR, 10 prints, 4 prints, etc... And then they can join another one next week, or next month, or next year.
Actually, Terri and I have already set up a very small print exchange; as soon as I print it up I'm trading one of my prints for her "box cameras" image that she posted a while back. I think that trading art for art is a great thing to do on many levels.
Later I'd like to do a BW darkroom only exchange with everyone getting a print from everyone, but to get it all started I'm up for whatever you guys figure out.