> They asked me for my credit card website logins, I provided them, and they took down all the transactions

Now that would make a juicy, tempting target for a hacker.

I really like the sound of this service, but I just can't bring my self to hand over login details for my bank accounts to anyone else.

Yeah, no matter how useful, you just can't give third-party services your bank logins.

Isn't this the same way mint.com and other similar services access your financial data?

This is the reason that I would not use Mint.com, yes. (Also it isn't available in my country.)

I'd like to see a similar service, but for merchants. That is, instead of alerting consumers to bad credit card charges, alert merchants to bad consumers.

For instance, there are consumers who if they decide they no longer what to subscribe to your service don't bother trying to cancel--they just call their bank and claim they don't recognize the charge, and so generate a chargeback to the merchant. (This is bad for the merchant because not only do they have to give back the money, they get hit with a charge back fee in the $15-30 range...in fact they get hit with the fee even if the successfully challenge the charge back).

The idea would be when merchants make a sale, they would report to the service a hash of the credit card number, the amount of the charge, what kind of merchant they are, what kind of good or service was purchased, whether this was an initial charge or part of a recurring service, and whether the charge was accepted or declined. If a customer of theirs charges back or refunds, the merchant would report that, and whether or not it was reasonable.

From this data, the service could develop a profile for each card concerning its refund and charge back behavior. The service could also develop a profile of the merchants, noting merchants that have unusually high charge back and refund rates, and so weight data from those merchants less when developing the card profiles.

Merchants, before accepting a credit card, could query the service and get a report on that card's charge back and refund behavior.

One might note that some of this seems similar to the systems the banks already have in place to detect fraud. It is, but those systems are not for the benefit of the merchant. They are primarily for the bank's protection and secondarily for the consumer's protection. The system I'm suggesting would be for the merchant's benefit and protection.

Presumably you suggested a hash of the credit card number, because passing them the actual credit card number would be bad?

Well, you couldn't use a hash for this. It would take hardly any time at all to generate a rainbow table which covers all possible credit card numbers.

It's been done before, I believe the website was badcustomer.com (no longer active). I think there's another one that's still active, but I'm not having much luck finding it.

There was a lot of negative press about this when it came out, I'm not really sure of why. It would probably be tough to overcome that if a similar service was launched.

The problem with that is that it would make consumers concerned about reporting merchants who were actually fraudulent.

In addition, many (most) merchants make it difficult to cancel so consumers don't even attempt.

Merchants brought this to themselves.

There are a number of consumers that abuse the chargeback process in order to get a service without paying for it, or to get a refund on something when they accepted an agreement saying it was non-refundable. It's pretty difficult for companies to fight fraudulent chargebacks, and I believe they get charged for it even if it's overturned.

This would make money, paypal and many other gateways close accounts based on the number of charge backs among other things.

This is a good idea.

What about looking up consumers via email address instead? Some consumers would get around that by using a different email address, but I bet the majority of consumers consistently use the same email address when making purchases online.