This is a big step for Stripe. I've often asked why they didn't have an integration with MaxMind or SiftScience already set up. They've been building their own behind-the-scenes the entire time! This feature is fantastic if you are a merchant and want to avoid fraud.
To me, the more interesting side of online credit card fraud is the merchant/payment processor side. Stripe has a cult-like following in the fraud world because it's known as the the easiest target. They make it so easy to sign up and process transactions compared to other services like Authorize.net/BrainTree/etc. They've shed this label recently, in part because the biggest forum thread discussing it was closed. The other reason was because it became so much more difficult. With this release, I think it's simply because they could identify accounts with high numbers of suspected fraudulent transactions. All the fraudsters were used to just signing up, running charges on their webstore with sock5, and waiting 2 days for bank transfers. Now Stripe can identify those transactions well in advance and assign each account a risk score. Previously, Stripe had to identify the account risk by sales volume, chargebacks, bank account provider, sign up IP, and every one's favourite privacy invader IESnare.
Fraudster's have one last shining hope against Stripe. Passing their card data to Stripe via API, instead of Stripe.JS/Checkout. Radar only works with Stripe.JS/Checkout. Setting up your own web server to pass card information prevents them from ever seeing any IP address except the web server. All you have to do to get them to be okay with this is to turn over a PCI self-compliance form. Rumour on the internet has it that there's a pre-built web application specifically for charging Stripe accounts via API.
I'm still looking for a job in fraud prevention friends at Stripe :D