Here are my thoughts, in no particular order:
1. If you look at all the forums here you'll see participation is in a wane - even in Pentax and Oly forums which have traditionally been extremely active.
2. This site has always had very few sports photographers on it. Certainly fewer who spend a good amount of their hobby time on sports. This as compared to DPReview or Fred Miranda.
3. Me. As you know I tend to be critical. My goal is to critique in the true sense - point out what is good as well as what is bad. IMO there are plenty of mutual admiration society types of places - facebook, myspace, photo sharing sites if all you want to do is share photos without the 'photography' part of it. But if you're going to post photos on a photography forum - especially a genre specific forum - sports, wildlife, people etc - I think it should be more about learning than just telling each other every shot is great. I know some people aren't interested in that. Some people just want to share photos for the joy of it and aren't interested in any constructive criticism - i.e. their interest in posting is not to improve their photography. So I think members of Steve's who may dabble in sports shooting just don't want to subject themselves to critique. They just want to be able to take the occasional sports photo, knowing it isn't perfect and not have to be told what's wrong with it. As any of us who do a lot of this know, sports shooting isn't easy. So it's very difficult for the occasional sports shooter to get good results (as compared to other sports shooters). They get results that are good enough for them and don't want to invest either in the equipment necessary to get better shots or the time necessary to improve their technique. Given this I think you find some very good people on this forum tend to keep their photo posts in gear sections rather than genre sections because there is less constructive criticism there. I don't see that as a problem - that's their choice and I respect it. But I think that's the reason they post there and not here.
4. For me personally I rarely like to just post "good shot" comments. Either the shot is great - in which case I like to say so, or I'll post what I like and don't like. But in that case I don't tend to post on subjects I'm not terribly interested in - example: cars, motocross, etc. Those subjects aren't of interest to me and I don't have experience shooting them. So there's not much in the way of constructive feedback I can provide. Because the subject doesn't interest me, there's not many "wow, awesome shot" reactions from me. Because I don't have experience I can't offer advice on how to improve. I think a lot of people here are the same way. If you look back, we have a number of shooters that specialize in a particular type of sport. So, they may not have the interest in other sports or just not the exerience to comment. Few members here shoot a wide variety of sports.
5. Mark switched to weddingns :blah:. Seriously I don't blame him though. If you're looking to make money off the hobby, wedding work is a LOT more profitable than sports work.
I agree, it would be nice to get more sports shooters here.