Take Linked-In, for example. I am on there (Profile here) and use it regularly for my business and to connect with people I meet and have interaction with. One of the things I like is that it tracks who looks at your profile and where you appear in searches. I was checking through my statistics today and it said 'Your profile has been reviewed by a Medical Writer at freelance'. So I clicked on the link to see who this might be. The first three names to appear on the list ('in order of relevance') are Chris Brogan, Hillary Clinton and Barack Obama!
(The Hillary Clinton link was especially interesting as I have recently being doing work on The Special Relationship - a film which deals with the link between Tony Blair and Bill Clinton. As part of this I got to work alongside Hope Davies who played Hillary Clinton in that film. Small world)
Remember, you never know who might be watching, listening or researching when it comes to social media