I did not expect this one: despite ongoing rumors that Viacom would snap up the music site for a massive $450 million, CBS will announce today the acquisition of Last.fm for $280 million in cash, according to an unverified source. The aim is to attract young people to the CBS brand.

The price is actually a little on the low side, at least in the current atmosphere of frenzied buying and ridiculous prices, but it's still a very good exit for the London-based music site.

Last.fm has deals with record labels like EMI, Warner and The Orchard, and it would surely have made a good buy for a record company or any big media player. Last.fm is also looking much healthier than competitor Pandora, which is being pummeled on all sides by licensing issues - with a dedicated fan base, it may pull through.

Looking for confirmation.

(UPDATE: LAtimes has it. Still surprised. CBS also just acquired Wallstrip, another bizarre buy for them. Anyone know what's going on here?)