Who sings that song that goes "you're just somebody who I used to know"?

Search: just somebody that i used to know

Why: I heard a song with that line today, but I know another song from a long time ago with that same line. Is this a cover or something?

Answer: Well, no. This is a whole new song by Gotye (featuring Kimbra).

Gotye is Belgian-Australian. His real name is Wouter "Wally" De Backer.

Source: YouTube

The More You Know: That other song I was thinking of was by Elliott Smith. The twist is that this is not the version I know - the one I know is a cover by someone else. It doesn't appear to be on my iPod (which I plugged in for the first time in 4+ months specifically for this), and I can't remember enough details about the voice to figure it out. It's frustrating. If anyone has any details, plz halp.