The problem with most mega-sites is that they really can't be all things to all people. Because they offer so much product, it's typically hard for them to really commit to developing any one niche or market. I think as long as there are really quality niche sites that can build a presence and really commit to their content, they will find surfers who would much rather join their sites than some mega-site that might only have 3 scenes of the kind of content they are looking for. You just really have to cultivate your own product and make it your own so that it can't be found anywhere else.