it all has to do with the "active members." check out the forum topic under "today's hot topics."
Membership Exodus

Please refer to the "Thats what she said" thread
http://www.chess.com/forum/view/community/massive-player-number-reduction?lc=1#last_comment

Those 9000 members are invited to mine. I've got a cocktail bar and can make a mean woo woo, then slap on some Chaka Khan, woot, party time!
What has happened to the total number of memberships on chess.com? The numbers have dropped dramatically in recent days - from over 25,000 to less than 16,000. What happened to over 9,000 members - or are the numbers being reflected a typo error?