A bunch of engineers at idealab did this back during the bubble. The idea was the saturate Pasadena, CA with $2 bills, particularly as retailers, lacking anywhere to put $2 bills in registers, tended to quickly re-release them.

We tried buying them a thousand at a time from banks. One time a manager came out to talk to us about it and asked what we wanted them for. We explained and his response was, "So we're going to get them all back."