The problem is that (if I understand you) you're making it so people can start web sites, host content, and charge a monthly subscription fee for access to that content.

That is the definition of a porn site and little else. Your market size is not the number of people who have fan pages on Facebook. Your market size is the number of people who want paid subscription fan clubs off Facebook. That's a very much smaller number. I would recommend not using the FB number because no intelligent investor will buy it.

You will have to prove there's demand, that isn't porn, for VCs to be interested.

If you think there is non-porn demand I would highly recommend swapping out the sexy model for a more "family friendly" example.