I know many stories like these. When I ask companies "Do you generate revenue via social media? Facebook, Twitter, G+ or anything?" the answer is always no. I would love to know about counterexamples if there are any.
http://www.jeffbullas.com/2011/08/30/11-social-media-marketi...
As anecdotal evidence, both of my late-teen/young adult sons have started using Old Spice deodorant since that campaign started.
Edit: I think Barak Obama's campaign would be another example of well-spent social media dollars.