I want to make it clear I have not seen one of these first hand, so I'm going based on my current understanding.
Essentially they're selling a list that contains your name, address, and other info that would be required in order to market solicitations to you. (I don't know if this includes phone number). It also includes some basic info about your credit such as credit range (500-600), etc.
From what I understand, it's not an exact score and does not include history. But for example, if a CA gets these lists and searches it for people they have in their records but not necessarily reporting and seeing you going up... they know you're working to fix your credit and know this is the time to get your attention.
Again, that is my understanding of how it works.... please don't consider this "cannon" by any means. 
@RadioRob wrote:I want to make it clear I have not seen one of these first hand, so I'm going based on my current understanding.
Essentially they're selling a list that contains your name, address, and other info that would be required in order to market solicitations to you. (I don't know if this includes phone number). It also includes some basic info about your credit such as credit range (500-600), etc.
From what I understand, it's not an exact score and does not include history. But for example, if a CA gets these lists and searches it for people they have in their records but not necessarily reporting and seeing you going up... they know you're working to fix your credit and know this is the time to get your attention.
Again, that is my understanding of how it works.... please don't consider this "cannon" by any means.
Well, I tell ya....someone out there has been selling a lot more than that! I have had 7 letters come to my house with offers for a mortgage refi! They know mymonthly payment...they know my cc balances too!
I just opted out.....Nosy "such-n-suches" !!!!!!!! 
Hey Mo...
We need to get some info about these guys and start selling it too.
Turn about is fair play, right?