Don't take those calculator value things very far. To be completely honest, this site isn't worth a lot and doesn't have much appeal for a buyer to come in and purchase it.
Facebook at 7 Billion is probably a little bitsy low as the company itself is worth more than 36 billion and brings in about 800 million a year in revenue.
This site is just a successful forum in the category that it is in, nothing more than that and not a very profitable category from an investor point of view.