My Paywall Start-up,Qasto
qasto.com
qasto.com
It's definitely a winning idea -- There are several other people in the sustaining themselves in this market, so while there is competition, I also know there is room for growth.
However you're monetizing it, I'd look to geo-target specific methods based on country.
Also, you can look at online marketing forums (warrior forum, wickedfire (maybe), digitalpoint, and blackhat world to advertise your services. Right now CPALead has a virtual lock on these industries in terms of locking premium content.
Also, facebook will typically either ban/warn you or delete your linking page if you link to protected material.
Also, your signup form gives me a headache. I'd recommend the standard flow down the page, or splitting it up on different pages.