Why do you hate it? It's an effective method of communication. For example, when we recently had the flood crisis here in Australia, and then got hit by that massive cyclone, it was much easier to spread news via Facebook to all the friends and family who wanted to check if we were safe and okay, than be taking a million phone calls. Especially since all networks were down in the disaster areas, and would only come online sporadically for a few minutes during the day, making phone calls impossible.
Also I think it would be cool to have some kind of achievement system updating to Facebook, like Steam has. It's pretty much like free advertising for the game and Nintendo. I mean, a person is always going to value a friend's word and experience higher than any marketing, so to be seeing a friend consistently achieving things in a game on a 3DS is an effective way to pique another person's interest.