The first thing that comes to mind for me here has to be of age bro/sis stories. Granted, the "we're home alone, let's hop in bed" types bore me for the most part, but still I just haven't been finding enough for the last year. Especially those that don't include what I already mentioned.
Beyond that, I agree with there not seeming to be a whole lot of Vamp fics, especially not well developed ones. Which could be part of the reason you're not getting too many hits, Acal - most people just might feel too let down by the underdeveloped ones and those that hardly if ever get updated