[myself248]

I played with Where's George? for a few minutes, then got bored. None of these things seem to have enough adoption to make it interesting.

If there were money in it, someone would throw OCR at the problem. Say, attach prizes to certain bills, or finding certain patterns of bills (say, two bills whose serial numbers are mathematically related a certain way).

[ianmcgowan]

If a government wanted to encourage spending, they could turn the lottery inside out by offering payouts on cash being spent by everyone. You take a picture of your money and if the serial number is today's lucky winner you get $1MM. Though maybe that would encourage hoarding instead? Cobra effect perhaps?

[Someone]

Euro coin tracking was a bit popular in the early days of the euro, as it showed how coins moved around Europe (you can’t identify individual coins, but each country has its own coins that can be used throughout the euro zone. Spanish and Italian coins move to Germany and the Benelux faster in summer than in winter, for example)

You can still play that game with new coins, but it’s less f visible now, as most coins are old and those already are well dispersed throughout the euro zone (and, of course, more and more people pay with a card)