At the same time millions are jumping on the social media bandwagon (Facebook, Twitter, etc.) for marketing purposes, their value is dropping like a stone. From Search Engine Land blog:

“In Edelman’s annual Trust Barometer survey, it was revealed that consumers are losing trust in each other when it comes to providing credible information about products or companies. Confidence has dropped by nearly half since 2008 leading to only about 25% of people trusting their peers and friends online for information.
“While the dip in trust was across the board, there was a large emphasis on social media.”

So the net result of the huge rise of social media, especially over the last year, has been to invalidate these media.
Well, they are still great for connecting and having fun.
Who do people trust the most now? Experts, especially if they hear the same thing from multiple sources.
This shift ups the importance of endorsements as distinct from testimonials in building credibility.