I wouldn't trust my mobile device or computer to handle every single monetary decisions for me. I want to control my own money, not the computers and devices. We have seen enough of iPhones being broken, keys from the iPhones being discovered, Android phones susceptible to malware, Governments trying to have a sneaky hand in all things ....
Remember Paypal rejected payment and donations for Wikileaks ?
What if you put all your eggs in a single basket (rely on bringing out your smartphone as a wallet) and something happens to that smartphone ? It's OS crashes and hangs ? It ran out of battery ? Accounts got hacked big time ? How are you going to pay after you had your meals in a restaurant if your phone had those crazy things happening ?
I would rather bring some cash along. Putting your money in one place is asking for trouble. When systems and things break, you are left with nothing on hand to help you out.
Smartphones as wallets by 2015 ? NO WAY !!!! I don't trust the technology. I don't trust the company and people. I don't trust putting all the eggs in a single basket. I trust myself more than them.
Don't forget, Paypal's spreading this myth to encourage more people joining them and giving them money because they are in the electronic money transfer business and if everyone uses only a smartphone as a wallet, they would have lots of businesses to do (not just them). This is simply a money making ploy.