I think that pixelation always had people who just just want to get there post counts up, and wouldn't take much time to actually appreciate the art. It started to become like a mainstream thing; "yeah, my friend's signed up, and so is the rest of the 'cool' kids from my school". Well, it was never that bad, but it seemed like people where joining just to say they did. Also, there was a point when almost nobody thought the art had any imperfections, and would always say that the art was perfect, which is a complement, but provides no help to improve the artist's skills.
Another big thing about pixelation, which I think was its ultimate downfall, was the rants. I think that when people start to challenge a society with opposing views, it can possibly work out for the good of the community. But seriously, its an art forum; instead of taking 30 minutes to type up a big opinion, why not just make some art expressing these views.
Also, a small thing I felt was a bad move was to make a bunch of different sections. In the old days there was serious and general critique, and that was it. I don't feel a board just for announcements or another board just for off topic threads was really necessary.
I believe that do to the combination of ranting and 'gizmos' on the site, pixelation started to lose quality content, and considering that a forum is based on content, it was probably not a positive thing for pixelation.
Now, I must get back to pixeling
.