We had a workshop about smart cards in my workplace yesterday:
http://www.hesca.com/about_smart_cards.html.
We had a guy in from another institution talking about their implementation, he had a lovely anecdote about the introduction of smart cards.
There were a number of Access control systems in place before the implementation of their Mifare smart card system. An audit of one of these access control systems showed that 60% of people authorised to enter a particular building were authorised via the mag stripe on their Tesco clubcard.
When a new member of staff joined, they had no staff card yet and needed to gain access to the building, the aministrator realised that Tesco printed their unique id to their card and he had a readily available database to use as authorisation.