Why do review sites do this?
 

They all want their links outside of the members area where everyone can see them. Wouldn't it make more sense to put them inside the protected area where they know everyone has already whipped out their CC and is probably willing to do so again?

Most sites want the link back to their site for search engine listing reasons I would imagine.

err no, more traffic more money....just becourse a surfer hates your site does not mean that they will hate all sites

Well they should also know on paysites they will get placed on some fake page with other links. Not like they will get any real benefit from it asking to be used as a traffic leak.