As if "the big three" (Equifax, Experian, and TransUnion) weren't enough trouble, this article: http://realestate.msn.com/Rentals/Article_bankrate.aspx?cp-documentid=5353032 talks about a fourth that's used by landlords to check the references of potential tenants. The good news is that they, too, have to send you a free annual report for your review. You can order it here: http://www.fadvsaferent.com/consumer_relations/forms/consumer_disclosure_packet.pdf. And, then there's also TeleChek/First Data. You can see what they have on you by going here: http://www.firstdata.com/support/telecheck_consumer_services/consumer_contacts.htm
They are many, many "credit reporting agencies." I wouldn't yet be overly concerned about any other than the major three with Innovis running a close forth.
Unless they are the "one" pulling your credit report! I believe you have the right to ask a potential "inquirier which agency they use. I've always asked my banks, auto loan and CC companies before applying.
Point I'm making is that one can't go running around worrying about every single data miner or scoring model. Priority should be placed upon the known providers of information.
What I found interesting was there was a specific bureau for renters. While most of the people who've posted lately seem to be interested in their FICOs for the purpose of buying a house, errors in yet another data bureau could keep you from renting a house or apartment. i.e. Even if you clean up your "big three," you could still be screwed by lingering errors from another report. I don't know how popular or widely used that report is and I think the last time I rented they pulled my Equifax report so, who knows. Your point of inquiring before applying makes sense, but asking at the time you are submitting an application won't give you much time to check or correct if you find out they use a reporting agency that you haven't checked already. Why don't they teach this stuff in High School?
Well, they're starting to! My son's high school is now starting classes in economics and personal finance. We also teach it as part of a Boy Scout merit badge now also...so times are changing!