[Jester]

I think it could be a variety of things. Part I think of is not enough users or users aren't active enough. It could be less activity in forums or other things not keeping their interest.

Another reason could be the owners or mods. Though I'm surprised Gaia hasn't shut down with all the bad mods running around I know lots left because of that. It could be sites shifting too much from owners hands too much or owners or admins promising stuff they can't keep. I think people get tired of we're going make a red ball item and never seeing said item. Sometimes they aren't even given an update which is the worst. People don't want to be left in the dark.