Interesting idea, however how will this differ from creating a facebook like page which hides the content like people do already?!

I think there is also user experience to factor in here. When I visit a bands page, take blur for a hypothetical example, I've already decided I like the band. When offered something for free to like them I've already make a concious decision to support them.

For your idea to be successful it will need to be embedded into sites where people already have engagement.

As a stand alone page it just won't work, unless you want to allow it to be branded per page, but that carries too much overhead.

Go for contracts with EMI or Time Warner and get your 'like > reward' product on hundreds of sites