We are aware of this, and if you can legally use social networks in your state, then you should us a pseudonym and not post any information that can be used to identify you.
On August 2, 2012 I left my house to do some contract work on a computer in another state. When I returned and logged onto the internet my Facebook page would not come up. Facebook responded to my question of why with a request for my ID. I sent them a JPG of my drivers license and sex offender ID from the state of Mississippi and was told I could not use Facebook and was referred to their terms. If you go there and look at their terms page Section 4 starts with:
4. Registration and Account Security:
Facebook users provide their real names and information, and we need your help to keep it that way. Here are some commitments you make to us relating to registering and maintaining the security of your account:
Line item 6 under that says:
"You will not use Facebook if you are a convicted sex offender."
I have started a petition at Change.org asking Facebook to change their policy.
Stop the removal of honest sex offenders from Facebook