Branded content in social media

Companies are moving more and more towards a marketing mix in which combinations of owned media (e.g., a website, online community or sponsored magazine) and earned (or social) media play an important role.

1) The question is how branded content and social media interact. How do retweets and Facebook likes help to lend credibility to branded content?
2) The motives to participate in branded online communities.
3) What people find acceptable social media behavior of brands: when (and why) do people give brands access to their Facebook network, to their tweets, etc.
4) What role do owned media (e.g., sponsored magazines) play in customer knowledge and customer education? And does feeling educated add to trust in a brand?