After watching the CNBC interview with Jack Dorsey and his demo of Square for the iPhone. Well I have a couple of concerns. In theory I love it but we are essentially at the start of the adoption curve, chasm, call it what you will. The demo looks pretty slick except for one vital bit of information. The signature.In the demo we see the interviewer sign her transaction for $3.00. All well and good until you picture this senario. I have Square on my iPhone and I find a purse on the floor, pick it up and swipe any cards I find. I actually have to have the authority signing, just a signature of some form (X marks the spot will do). The SMS/Email receipt will go to the signing authority but the transaction has been authorised (in my eyes). There’s no verification of the three digit security code so it won’t fly in the UK until that’s resolved. Finally is there a limit on the upper amount of a transaction, the website suggests “$0 to $60 in under 10 seconds” but that’s no definitive answer.Also, where are the scan details stored? Externally over SSL or on a SQLite database? I can envisage Square hacks coming out to query any saved data on card info.Like I said at Barcamp Derry in October. Paypal was not originally designed as a web payment system, it was to prove the concept of one shot cryptography between two Palm Pilots. It never made it as a Palm Pilot system for the simple reason that no one was prepared to use it. As much as I love the concept I can’t see it flying as the wave of public concern will be too great.I’ll keep an eye on this one.