You've spoken, we've listened!  We've opened up private messages to allow any user to send any other user a private message.  However, we've also added the ability for a user to choose to only allow private messages from only their friends, if they wish.  We've also brought back the ability to block individual users from sending you private messages.

By default, any user can now send any other user a private message.  If you wish to restrict who can send you a private message, you can do so on the "Edit" tab on your account page. Also, there is a new "Blocked Users" tab on your Messages page that allows you to add any other user to your block list to prevent them from sending you private messages.