BuddyPress.org

i think Trent solution is good but maybe i think in this case doing a plugin is simplier than it :S.. for every update (if you use svn for example), you’ve to reedit the code..

adding a function in your plugin that define if current visitor is logged in ( look at is_admin() for wp and some other bp conditional tags) and define if the visitor can visit pages or not..

i think it’s possible and easy..