[jliptzin]

That's true, things that sound simple on the surface often turn out to be pretty complex in implementation. I think that the number of people making purchases without cell phones on them is converging towards zero and will be there soon, so I think it's safe to think about these systems now.

What about implementing a 2FA system for larger purchases (online or off), implemented in an app on the consumer's phone like google authenticator or sms? Swipe your card at checkout, if amount is > $XX (or otherwise suspicious according to current models), prompt the buyer for a one-time code from SMS or an app. I use the same system when logging into gmail, my bank account, etc - I'd have no problem (and would even welcome) a similar system when using plastic. It's at least a lot more convenient than having the txn declined and your card disabled until you call their security hotline. This way, thieves would need to steal your card and your phone to cause damage.