yea I think Mark is right. There was a limit imposed to stop people "freeloading" forever and sending strategic "winks" to full members to get out of supporting the site.
A site for 63,000 members and 30 million hits per month requires substantial infrastructure and support to maintain it, as well as a high investment in advertising to bring in constantly more new members (replacing those who leave). It's a shame most people can't understand that and they post their email address, phone number, facebook link etc on their profiles, forum posts, photos etc.