I've worked a bit in the industry and around the industry, the worrying thing for me is that it doesn't seem to be working for anyone apart from equifax/experian/call credit.
I have separately worked with one of those companies with a client and their IT staff were utterly incompetent (I won't say which). Loads of different sites, lots of little fiefdoms, utterly inconsistent security policies on each site, blaming everyone but themselves because only half their sites could access a video on a major commercial video provider (not-youtube). We ended up having to host it on AWS cloudfront as none of them had blocked it yet. Their sharepoint could only host a 50mb file, which made their CEO look like a blockhead in the 20 min high def video.
Utterly incapable of hosting a simple video file so all their staff could access it in 2010.
I've also worked with a company one of those companies acquired for $100 million+, holding millions of people's personal details in the UK, with some very sensitive data. Some of the worst IT engineering I have ever seen, a bunch of tools written by the worst out-sourced IT teams I have ever seen (if you've ever worked with C#, these idiots made a project per .cs file. Yes, PER CS FILE. They also wrote the worst SQL I have ever seen, all of the stored procedures seemed to be duplicated but the duplicates had op_ before them. I eventually realised the op_ stood for optimized! They were still terrible and half the program used one set of SQL, the other half the optimised. Whenever I re-wrote one of these 'optimised' queries, I usually knocked it from seconds to milliseconds. Outsourcers in the naughties really did suck that bad, young 'uns).
We've given up huge amounts of privacy, but the scores are utter bullshit and the 2008 crash show what a load of nonsense they are.
A friend even told me at uni he'd got a £1000 loan out to get a good credit rating. You just put the money in an account, pay the capital off every month, lose a little bit of interest and in 2 years you have a shiny credit rating even though it means zilch.
equifax/experian/call credit basically get given all our personal spending habits for free, sell it on to everyone else for crazy money, don't add anything to the economy and as far as i can tell, are a huge security hole.
EDIT: Another anecdote on how incompetent these people are, a couple of years ago someone used my details to scam a few free phones. I got alerted to it when I started receiving insurance contracts for those phones in the post. The phone companies sorted it pronto, almost immediately admitting they'd been scammed, but I wanted to make sure my credit rating hadn't been trashed. In the UK these agencies must provide you with a credit report for a nominal fee so you can check for incorrect details, so I applied to the big 3.
One of them accused me of trying to hack their system because I'd forgotten a security question, eventually told me to fuck off after passing through various layers, then sent me a letter saying they'd detected a hacker trying to access my details. No, you idiots, that was me. Still never got my report from them.
Yes, they still use security questions.