Pop as a fandom is actually fairly large and yet fairly cohesive. Not on the scale of something like HP of course, but it feels pretty there. And, whatever you think of RPS, most popslashers are legitimate fans of the media as well. They buy the albums and the DVDs and pay obscene amounts of money to go to charity events.

I find that the HP fandom is so large that there are practically BNFs by pairing. So that you'll find someone who's very well-known in Snape/Harry circles, but the Harry/Draco people won't have even heard of them.