Social search has been attempted so many times.

Google tried it in 2009, failed. Microsoft tried it in 2013, failed. Startups across the board have tried it.

I think it is because "social" usually implies to a user that they are searching for a person, not the content they create. And previously, there wasn't a ton of UGC that was relevant to a query.

Disclaimer: I'm a You.com employee working on search.