There is some debate over whether CBS bought last.fm for the community, or just for their technology. I doubt they paid $280 million for the technology. Their recommendation technology doesn't seem that sophisticated; their advantage, like Netflix's, is in the sheer volume of data to which they have access. If you know every song someone has listened to, it's not too hard to figure out something to recommend. Maybe CBS wants the respected brand name of last.fm to attach to a new video-based recommendation service, but I don't think the technology behind the service was a major motivator of this purchase.
One major concern I had about this merger was how the recent hike in internet radio fees in the U.S. would affect last.fm, when it was owned by American CBS. I was under the impression that last.fm was not affected by this recent scandal because it was a British company. Turns out this was half-true, as last.fm, under British law, was forced to negotiate directly with record labels, and has deals with several majors, with more deals expected to close soon. So with these deals in place, the internet radio royalties that threaten to destroy other internet radio providers shouldn't be an issue for last.fm.