I was recently interviewed about my work on FareBot for a couple articles discussing the privacy of transit card systems:
The Bay Citizen: Clipper cards reveal travelers’ whereabouts to police, lawyers, apps (San Francisco Bay Area; October 2012)
Crosscut: Smart card: What your ORCA never forgets (Seattle-area; February 2013)
The Daily: Researchers question U-PASS security (University of Washington, Seattle; February 2013)
FareBot was originally conceived as a proof-of-concept demonstration of how many existing transit payment systems are compatible with new NFC phones. It was a pleasant surprise to hear from many people, including people outside the tech industry, who use the app to check the balance of their card before heading to the train station or bus stop.
Removing detailed trip information from these cards while keeping the balance readable without authentication is a good compromise that balances privacy with utility.