If you really want to have your own Facebook look alike, head on over and grab the theme. It’s free.
*Updated July 6th, 2010*
As has been pointed out by a commenter, this theme appears to no longer be available. Even when browsing the BuddyPress website and performing a search for the Facebook theme, the results point to the same link, BuddyPress Social which is part of their Premium theme selection.