Why can't the money be followed?
If the NSA is such a powerhouse with billions of dollars of assets to track every electronic communication, why aren't they focusing their entire resources on people like the sellers?
Or is it like the TSA where they just hassle the completely innocent people at the airport for show while the real criminals take other paths.
The FBI would be investigating this, and they are probably actively following these transactions right now. But since they are a criminal investigation agency, they will be focused mostly on carefully collecting evidence, so that it can be used in trials to obtain convictions.
So: this exposes a gap in how the U.S. federal government approaches the Internet. The NSA is willing to react in real time to threats, but they don't care about crimes like carding. The FBI cares, but they seek to collect evidence, not react in real time.
The result is that when it comes to real-time reaction to cybercrime, companies are largely on their own. I'm sure Target is spending a good bit of money on cybercrime and cybersecurity consulting firms right now.
Because they didn't invest that kind of money to find the logs in a haystack that are eastern bloc cyber criminals. They are looking for a needle in a haystack dammit. A needle. (and possibly if some of their wives are cheating on them).