Ok, this is a bold-faced lie. It seems American soccer personality Grant Wahl mentioned this possibility on his satellite radio show this morning, calling it "informed speculation" (thanks, Tim, for the info). Now, I'm not sure what "informed speculation" might mean, but there's been absolutely nothing else linking Dempsey to Villa.
Granted, Dempsey hasn't exactly made himself indispensable to Andre Villas-Boas, particularly after Lewis Holtby's arrival midseason. In fact, this all may have started from a rumor perpetrated by Ian Darke, who said on Twitter that "reports" are saying Spurs have made Dempsey available for transfer.
But we still have the usual stumbling blocks: age and wage. Dempsey is 30 now, and if there's one thing we're certain of is Paul Lambert's philosophy: buy young and buy cheap. And that's the other part of the puzzle. Tottenham blog Cartilage Free Captain estimated last year that Dempsey's wages were likely around £70k which, while not ridiculous, is still likely too high for the slashing Villa are doing.
Point? Rumor that Dempsey is on the market + American soccer personality needing to talk about Americans + Spurs wanting Benteke = nice little connect the dots. It makes sense in theory, but it's highly unlikely.