An IP address isn't unique to a device as they often change, a MAC address is unique to each Internet enabled device. So some of the facts in the article are wrong. I guess a smart phone in the hands of dimwit is a bad idea but if you know what you are doing then it should not be a problem.
The old adage is true, you don't get something for nothing. If your prepared to join every unlocked wifi network available then you have to be prepared to give away all your pass codes.
Simon.