forums typically slow down during summer periods, particularly when the weather is good as people are often out doing other things instead. of course there are exceptions such as sites based around summer or outdoor activities or sports, or if something in particular is happening that may spark interest
this particular sites front page is full of reality stars, big brother, x factor, towie and stuff like that, and soap opera tv stuff, so it's going to naturally attract a certain type of person. the music on the front page is more often than not based around xfactor type acts and singers who rely on teams of people to create music and videos and stylists, or rappers of the commercial nature. so you aren't going to attract many serious music fans with that type of front page
most of the main prime time network US tv shows are off during the summer period for similar reasons, and likewise big album releases usually avoid that period. the uk singles charts recently had one of the smallest changes to line up in history, and the number 1 slot was held for a large chunk of the year so far by an actor who's doing little more than talking over the top of a tune based on a track from 30 odd years ago. so right now the music market is a bit stagnant
facebook is also taking it's fair share of forum use, with people finding groups that satisfy their niche requirements more, and it's easier to setup a group than start a forum, so of course some will tend to go that way
one thing that the longer term members will perhaps spot is that those who are typically quite active for a short period, particularly those quite vocal about particular artists, usually have membership of less than a year, and then they disappear and a new batch of names turns up and then disappears, giving the impression it could be the same users returning with new names after being banned. there's been a few recently that fall under that category. there is of course the appreciation sub forum so if people want to fanatically post about a certain artist and avoid any negative comments, they can do so, yet they don't, which makes many threads sound suspiciously like they are created simply to spark a certain reaction, which at times will lead to the loss of more members