Not sure if FB assumes every one to sign up all by themselves wit FB! Or they assume FB as online passport (taking pride about emselves:P) . According to them, " its never inviting some to FB, basically its just Finding some one FB!" :P ;)
wat ever might be, today i felt like inviting some one to FB, jus fr the matter of fact i knew th person is not in fB! And i couldnt believe myself tat it took a google search to find how to invite a frnd to FB!
As you might expect the invite MAGIC button to be present in the page where you see ur frnds, thats after clicking the "Friends" link on the left of the page, you will be surprised to find it otherwise! Unusually it comes only after you click the "Edit friends", on the http://www.facebook.com/friends/edit/ page as the "Invite Friends" link.
The funny part is the url to invite frnds is quite simple its http://www.facebook.com/invite.php . In such situations i really get to love the REST URL's ( not tat i know much about REST, still i could visualize its importance!) Say in a rest based world the URL will be http://www.facebook.com/invite which ppl might guess best in rest based world :P ;)
P.S. Infact, After all this i never went ahead inviting her, all i did was write this blog! Good luck to others!