Would there be interest in a socially oriented site to let GMs and players set various preferences for a game and find each other kind of dating site style? Was also thinking, too, such a site would let people submit reviews and generally discuss related topics. Third party integration (to what extent I'm unsure) with obsidian portal and roll20 would streamline a "find a group then start a campaign" kind of flow.
The need I see is reverse that of those kinds of sites I would integrate with. There are a few good places like roll20 and OP to start a campaign around. However, I don't see many to find a group either for virtual table top or real life outside of disparate tools like how certain PFS VOs will set up sites for just their state. Facebook lacks the granularity of such a platform. This would be more of a focused tool toward those ends.
Initially, the it would focus on Pathfinder, the system with which I'm most familiar. I would be looking to bring on GMs and players to help flesh out good matching criteria who grasp the nuance of a particular system once it's up and going. I would see D&D 5E being next unless something changes that.
To give a bit of credit: the new guide by Abraham spalding about Optimizing your GM made me realize there's nothing really good out there for matching these quirks from what I've seen. I recommend it!
This is actually a really neat idea. If you want help I am afraid I can offer little, though if you need to raise some funds for it I'd be glad to through a hundred or two your way via Kickstarter or something to see this happen.