Facebook hit 350 million users last night, the site announced to its users in an open letter from founder Mark Zuckerberg. Also announced was the removal of 'regional networks' (cities, countries, etc.), which were found to be a security and privacy hole that was not well understood by users. Previously, all members of a regional network had complete access to each other's information as a default choice. Now, users will have the choice of making their information available to friends, f...