Sam Sethi at Blognation UK has a scoop: apparently, he got a preview of a new instant messaging app for Facebook — and according to his description, it doesn’t require you to download or install anything, or to register, as many Facebook apps do. You just sign in and use it. At the risk of sounding like a Facebook fan-boy, despite the ugly interface I think this could be huge.

I think it could be good not only for Facebook, which has been missing real-time chat — making do with messages and “wall” posts — but for instant messaging as a whole. Like Sam, I see it as a way of doing an end-run around the fact that you still need multiple IM clients to chat with all of your friends, who might be using Yahoo or AIM or MSN or Skype or GTalk

“No more MSN, AIM, GTalk, Yahoo chat — one instant messenger for all your friends.” All your friends who are on Facebook, of course. Still, it sounds like a pretty good solution to a Balkanized IM environment. And it could stand to make Facebook even stickier than it already is.