Several of the sites in my RSS reader have ads for various quack medicines and supplements. One of these was something like "acai--an Internet scam?" and lead to a fake consumer reporting website, where they decide that at least one acai berry company is legit, complete with directions on how to order a free trial (just pay shipping...) from there...But when you try to leave the site, you get pop-ups and redirects that try to prevent you from leaving.
I cannot imagine this ever actually working to sell product, and I would think that it would be counterproductive-Imagine someone taken in by the scam, but short of money until payday. They try to leave with the intention of ordering later...and the popups make them change their mind.
(I would also be nervous about visiting one of these sites with a Windows computer)