[hackuser]

Eliminating immediate feedback about failed transactions makes things harder for everyone the fraud detection system identifies, both fraudsters and the many false-positives. And the false-positive rates seem very high, IME; it seems like I and everyone I know has encountered that problem multiple times.

Imagine that you place a legitimate order and they don't tell you it failed; how do you find out? Days later when the order never arrives? That would result in very angry customers.

[erikpukinskis]

There's nothing inherently bad about very angry customers. It's more about how you handle them and whether you are continuously looking for ways to decrease them in number.

In this case, the idea is these are people who tripped red flags for you, and upon investigation didn't give you any reason to believe they were legitimate orders.

If you're really worried, you can contact them and ask.