Why did Obama's off-the-record/on-the-record/off-the-record snipe at Kanye West make news? Adam Serwer, writing at the left-leaning American Prospect, offers one theory. He says that it's got nothing to do with Kanye, but everything to do with what the Professor Gates scandal meant to the right:

Let's just ponder for a moment that, at some level, people on the right think that [Kanye] West interrupting [Taylor] Swift in some way analogous to a man being arrested on his own front porch for being rude to a police officer -- the similarity being that, for the right, in both cases white people are the targets of racial victimization on the part of blacks. Also bizarre is the right's apparent shock that Obama actually criticized West -- as though the president simply sides automatically with the black person in a given dispute. This expectation of knee-jerk tribalism from conservatives on behalf of Obama actually says less about the President than it does about them.
Could all this have an intentional leak, calculated by a president aware of striking the right balance with Americans? Serwer thinks not:
At any rate, since the exchange was meant to be off the record, we can put the rest the equally silly hypothesis sure to develop in some circles that Obama's comments about West were a clever political ploy to reassure white voters.