Another day, another curious acquisition. When CBS announced it was buying Last.fm, a social media platform that does not appear to be making much money, for $280 million, it certainly gave pause.

Last.fm is one of those irrevocably trendy Web 2.0-ish properties, complete with unknown business plan, a functionality depending greatly on user interaction, a bevy of competitors, and a media-designated tagline comparing it to the incumbent in the space: “this generation’s MTV”

Last.fm is an Internet radio ...