Plus, you can win prizes. I just signed up, but my friend chapstickqueen has friends who have won lots of different prizes, including iPods. Seriously. Of course, most of the prizes are more like gift cards and movie tickets, but I wouldn't say no to that either!
You don't have to buy anything, you don't have to click certain links. Apparently there are certain "winning times" and if you happen to be the first person to search after the winning time, you win! (you can only do it ten times a day, so you can't just sit at your computer constantly searching)
Oh, and apparently, if your "Blingo Friend" wins something, you win one, too!