Not all websites in Social Media are created equal. I think a basic guidelines should be posted in all sites.
1. Facebook is one my least favorite sites because it is least secure. Facebook has nasty tendency of selling data. See those annoying ads on the side they are specifically targeting you based upon past buying habits. A. Facebook all that private information on this site is public and shared not by the friend list. Anyone who write down a tag and view it. C. Nothing is private and putting addresses and locations is bad.
B. LinkedIn is good there are adds and topics are of interesting. It is slightly more secure than Facebook. It is more professional.
These are examples that social media sites are needed guidelines for what they can be used for.
Most employers are looking at these accounts to see what kind of person you are. I am against this because it is invasion of privacy. If a site completely social it is none employer's business. Since there is no Laws against it. It is up to user to be aware what the company is doing.
I would like it for social media website state that all content on the servers is subject to sale to advertisers.