Last night as I was watching "Inside Edition", they reported on call centers being run from prisons.

There are currently 17 states that allow this, but only two states require the prisoners to tell you they are calling from prison. In other words, the next time a telemarketer calls trying to sell you magazines, they may be calling from a prison call center.
One of the prisoners called a home and the 15 year-old daughter answered the phone. He deviated from the script and got the girl's name, age, address, and a physical description. Days later, she received a "pen pal" letter in the mail from another convict in prison with the man she spoke with.
So, be careful, especially with your personal information!