[khnyny]

You don’t need a stamp. Use your printer and print on the bill anything you want to say. Print “Geitner Is A Tax Cheat” right over the sig that’s there now. I wouldn’t use red ink. I would use a green ink to blend in unnoticeable in order to get as many into circulation as possible.

That's a very BAD idea - don't use a printer. A printer can be tracked, but I think you know that already.

[khnyny]

Sleuths Crack Tracking Code Discovered in Color Printers

http://www.washingtonpost.com/wp-dyn/content/article/2005/10/18/AR2005101801663.html

It sounds like a conspiracy theory, but it isn’t. The pages coming out of your color printer may contain hidden information that could be used to track you down if you ever cross the U.S. government.

Last year, an article in PC World magazine pointed out that printouts from many color laser printers contained yellow dots scattered across the page, viewable only with a special kind of flashlight. The article quoted a senior researcher at Xerox Corp. as saying the dots contain information useful to law-enforcement authorities, a secret digital “license tag” for tracking down criminals.