Not that it's a showstopper, but Photoshop has built in currency detection based on the EURion constellation, a pattern printed on a lot of currency worldwide to help prevent counterfeiting. Kind of cool.

http://en.wikipedia.org/wiki/EURion_constellation

Edit: Of course I learn after posting, apparently EURion is not what Photoshop looks for, but rather a digital watermark. The detection is given to Adobe as a binary from a security firm.