The new updates to the iphone and new droids (and other smartphones) are including the new feature to be able to pay for your purchases using your phone. While it is very convenient to do so, just carry your smart phone, it is also pretty scary. Think about it. Your smart phone already contains your emails, contacts, personal data on yourself, probably your CC and bank info. If your phone breaks or gets stolen or hacked? Big. trouble.
Now I am a smartphone user myself, I use a HTC Incredible, and it holds my emails and personal data. But I am pretty wary with it.
Just some food for thought.