When this feature was first added to photoshop it caused a noticable delay when opening files or pasting content from outside photoshop. It was possible to disable the check by removing a DLL from photoshop and get the speed back to normal.

Somehow I don't think this feature has done much to discourage serious counterfitters, it's just annoyed legitimate users, especially as there are pefectly legal ways in which an image of a banknote can be used.