This is very similar to the Groupon model... you get a deal (or a thing) while being being motivated to spread the word. Not 'sharing' so much as promoting. You're being inconvenienced (paying) and it allows you to edit the text.. so you can just say.. "I'm tweeting this page so I can read it rather than pay them. Sorry." I don't know. Not sure if this is the final iteration but very cool that they're trying to figure out how to put value on content other than banner ads. Hope they figure it out.