Behavioral targeting is all the rage in online advertising. The technology aims to show ads to Internet users based on the sites they visit and the actions they perform, rather than targeting words they search for, as Google does, or matching advertisers' desired demographics to a site's audience, as most banner-ad purchasers do today. ValueClick has introduced its own product, in competition with AOL's Tacoda and Yahoo's BlueLithium. But ValueClick's executives may not be particularly confident in the product — if rumors are true that they're talking to startup Revenue Science about an acquisition. Revenue Science has raised more than $70 million in venture capital, and recently appointed former ValueClick executive Jeff Hirsch as its CEO.