There are a few paper-based analogs. I seem to remember reading of a handful of towns that created there own voucher (currency) that could be used in all the shops in that town. Maybe Ithaca NY (Cornell) was one?
I believe ithaca uses a time-currency worth about ~$10 an hour. There's also Berkshares and a few others. All of said currencies come with a socialist hook, however.
My question is, even if you load BTC to your smartcard's address without connecting it to your computer somehow, how does the card know how much is on it? Seems to me it'd be up to memory and luck to make sure you didn't overdraft, which would end up sending an invalid tx anyway. More importantly, how do you set your pin without a central authority doing it for you? I think it's also worth noting that if a card continuously re-uses a single address, then it kinda kills your privacy too.
On the merchant end, assuming physical sales, there's still the problem of integrating a bitcoind backend for register and accounting software, and exchange risk. It seems to me CAO/ICS systems would be less affected, if at all except for the inherent exchange risk involved.
Protecting against double spends = easy
Protecting against exchange risk = not so much
Protecting against arbitrary government confiscation and dealing with accounting conversions = jungle gym
In Greece I think all the disadvantages are moot. Greek business owners currently can't get loans, greek people have no money to spend, and the value of the Eur is evaporating out from under them both in government debt and inflation. Anything that would allow them to easily manage their business or even do business at all would be nothing short of deus ex machina for them, and it's not like they give a damn about complying with government tax regulations or anything. They would like nothing better than for the EUR, the ECB, the IMF, the unelected European Commission, and their own unelected government to hurry up and die so they can get on with their lives.