A friend was posting about them on FB and I was inspired to join in and buy a pack! You can register your deck and track how far they go online, presuming the people down the line go to the website and say where it's been. So, say I played the card today about paying bus fare. Then that person goes on a trip and pays for a fare in New York. That New Yorker logs on to the site and says that the card has been to New York before they pass it on ...etc. It's pretty cool. :)