Curiosity got the better of me and so I held up a bright light to my badge. The internal antennae were readily apparent. RFID it is, I guess. Then I simply peeled the two layers apart to reveal the metal inside. Note the fake smartcard print on the face:
A total of six little lines run around the edges of the badge and end up connecting to a strip just below the Taj image on the right. A tiny slice or pin-prick through these lines would kill the tag without any obvious damage. I wasn't particularly careful because, well, I was feeling impatient and a bit cavalier. A clean job can be accomplished by sliding a razor gently and repeatedly along the edge of the badge and peeling up the label on the back, then lightly slicing the metal lines, then gluing the label back in place and applying pressure. Of course my badge rarely worked anyway and I refused to take it out of it's little plastic pouch (when it wasn't in my pocket) so this is hardly a burning issue. In fact, after several attempts to read my badge on the first day HP actually asked me to type my info into their system by hand…had I been more patient, and the card more reliable, I would have first tried to read the thing and see how the data was stored. Maybe next year.
I also noted that someone left themselves logged into the badge station in the afternoon when there was just one bored guard standing around. That seemed especially sloppy to me and made me wonder if anyone had ducked behind the desk to print their own badges on the sly.