But is it likely? "If it were an older system, it's possible," acknowledges Louise Casamento, director of marketing at PMS vendor Micros Systems Inc. in Columbia, Md. In the past, people weren't as conscious of security, and ISO card readers weren't readily available on the Web, she says. But Saflok's Scott says it's not likely. "I've been doing this for 15 years, and I've never seen it," he says, adding that Saflok's system doesn't even have an option to allow the encoding of credit card data onto its key cards.

"I would have to say that it [would have to be] a very old system -- and they are still out there -- that may still allow this," says Jocelynn Lane, vice president at VingCard AS, a vendor of electronic lock systems based in Norway. But, she adds, "we've never seen them compromised." Certainly no system would do it today, she adds.

The only situation where Lane says travelers might find sensitive personal information on card keys is when they're abroad. "There are locking systems in Europe that, when you check in, let you enter a credit card, guest name, everything [on the card]. But never in the States," she says.

"There are probably 60,000 hotels in the U.S. right now. To say no one has done it would be presumptuous on my part," says PLI's Goldberg. But the chances of guests running across the problem, if it exists at all, are slim. "I would never check into a Holiday Inn and worry about it," Goldberg says.

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