I was off here for a while but I do feel like on most threads you are generally seeing the same group of about 50 blokes posting. I feel like the bitcoin probably has weeded some people out (like it did me for a bit) but hard to say if that really makes much difference, I think it's just the nature of forums that you have a small group regularly contributing, a slightly larger group that posts semi regularly, and a majority that post rarely or not at all. You'll see this if you sign up for any other kind of hobby forum
