My employer has recently issued us all with new identity cards as one
building, on another site I never visit, has had its entry system
changed from a swipe to a proximity entry system, similar to Oyster.
Apparently, a number of staff have suffered damage to their Oyster
cards, as they have placed them in wallets etc. next to these new ID
cards.
The guy I share an office with, a computer support guy who speaks in a
language I rarely understand, tells me this is normal for Oysters to
be corrupted in this way. He went onto tell me, that if you place two
Oyster cards together in a wallet, one or both of them will corrupt.
Proximity entry to buildings is becoming more normal, apparently a
several of cash-strapped universities and colleges in the London area
are swapping their systems as it is cheaper, no doubt other
organisations will in the future. As I don't need, an Oyster card, I'm
not that concerned, but this might be interesting to watch in the
future.

Neill