Until last night, Top Friends by Slide was Facebook's third most popular widget, judging by daily active users and installations. Today, Top Friends is no longer on Facebook at all. News.com says its because pesky Canadian Byron Ng discovered a security loophole in the widget that allowed any user with Top Friends installed to view more profile information — birthdays, gender, and relationship statuses — then Facebook allows strangers to see. Ng discovered a similar loophole in SuperWall, an app made by Slide rival, RockYou. But RockYou already fixed the problem and SuperWall remains on the Facebook platform. No word on whether this little tidbit has Slide founder Max Levchin in this hospital from punching holes in a wall or two. (We hear the rivalry is a little intense).