brethren does throwdowns, and they are fun. Some really good photographers too. It really is inspiring sometimes, and I end up cooking things that I normally wouldn't have before. They have prize sponsors, and give away some pretty valuable items. We are probably too small for that at this time, but something to shoot for. I would be somewhat skeptical of the participation. Brethren is a huge site, and sometimes they will only get 4 to 6 entries. Other times there may be 30.
I do think for it to be active there most likely has to be something up for grabs other than picking the next category. Even if it's just a bottle of rub or sauce that maybe isn't available widely.