But the _spirit_ of social media is to publicly share information for specific types of social interactions. I have always felt that examples like job recruiters researching applicants' facebook content is morally corrupt, although I don't expect it to ever stop.

For a crude analogy, let's say you're having a yard sale in your front yard. Everything for sale is on public display. How would you feel if a company rep from xyz corp decided they could make a better profile of you by judging all of the contents of your yard sale? It's publicly available data, but is it appropriate?