Seems that Iranian activists are using banknotes to relay messages:
Make sure to check it out and see all the examples of the modified banknotes.
From the post:
'Anti-government activists are not allowed to express themselves in Iranian media, so theses activists have taken their expressions to another high circulation mass-medium, banknotes. The Central Bank of Iran has tried to take these banknotes out of circulation, but there are just too many of them, and gave up. For the activists’ people it’s a way of saying “We are here, and the green movement is going on”.'
Lets see what we get when we analyze this from a data communications perspective: