On December 23, 1998 Hank Estrin's Where's George?, a website that tracked the natural geographic circulation of American paper money, became operational.
"A hit is when a bill registered with Where's George? is re-entered into the database. Where's George? does not have specific goals other than tracking currency movements, but many users like to collect interesting patterns of hits, called bingos. The most common bingo involves getting at least one hit in all 50 states (called "50 State Bingo"). Another Bingo, FRB Bingo, is when a user gets hits on bills from all 12 Federal Reserve Banks.
"Most bills do not receive any responses, or hits, but many bills receive two or more hits. The average hit rate is slightly over 11.1%. Double- and triple-hitters are common, and bills with 4 or 5 hits are not unheard of. Almost daily a bill receives its 6th hit. The site record is held by a $1 bill with 15 entries.
"To increase the chance of having a bill reported, users (called "Georgers") may write or stamp text on the bills encouraging bill finders to visit www.wheresgeorge.com and track the bill's travels. Bills that are entered into the database, but not marked, are known as stealths" (Wikipedia article on Where's George, accessed 05-04-2009).