On a recent trip to San Francisco, I found out that they were still giving away their new, integrated, cross-agency (and boy, with Muni, BART, Samtrans, Golden Gate, Caltrain and AC Transit in the city alone there are a lot of agencies to cross) smart card, called the Clipper Card. I stuck one in my pocket and tapped on to a ferry, a bus, a train, a subway, and a streetcar. Except, it wasn't quite the tap-your-wallet convenience I've come to associate with my Charlie Card.
So I experimented. Clipper and LA TAP card worked fine. Clipper and Charlie? Not so much. And a week later in Boston, well, the Charlie Card didn't work well here unless the Clipper was out of proximity. It's too bad; proximity cards are very convenient, speed transactions and boarding, and can make a multi-agency hodgepodge like San Francisco (to say nothing of LA) somewhat more seamless. But, really, someone should assure that the cards' frequencies don't interfere with eachother.
(Or, perhaps, I can dream of a day when transit agencies nationwide are all on the same frequency, and system. Ha!)
(posted from iPhone; will clean up later)