In regards to gaming chat I think Nintendo have changed so much since the Gamecube that a lot of people just arent interested in them like they originally were when they first joined and with forums being less relevant now, the kids who do like Nintendo these days arent really joining up.
As for normal chat, its just become boring for me. A lot of comments just seem to get ignored in favour of the usual poster groupings and conversations are starting to become predictable. I didnt bother logging in for a couple of months this year and I didnt feel like I was missing anything, the few people I actually enjoy talking to here these days I could chat with elsewhere.