> I'm kind of surprised no one has started a service for merchants to warn them of chargeback prone customers (there are people who go straight for the chargeback without even trying for a refund first).
There are plenty of such services. You don't see them because they don't normally operate on the merchant level, they operate on the IPSP / processor / card company level.
The reason why they don't usually operate on the merchant level is because that would allow a merchant to pollute the pool with their 'known good' cards to stop people from buying a product with competitors. You have to wonder when you buy this information as a merchant whether it is clean or not. But when an IPSP / processor or card company uses their aggregate knowledge then it starts to be really useful.
You can do AVR checks and so on all by yourself as a merchant but most if not all reputable IPSPs will have an anti-fraud system in place that does all kinds of checks.