my experince s***ests that the most efficient vector is to associate some adware with the content that users would love to get. Imagine, say, nearly any office worker at least once wanted to convert pdf back to word. So you get a free program like that and bundle it with adware. The scheme might be legitimate, your adware is announced, users agree by failing to uncheck the box which is checked in advance, everything is pretty legitimate. Example of such adware scenario is adsmatte, you may leran more here [url]http://soft2secure.com/knowledgebase/adsmatte[/url]