It doesn't really have capabilities, it's just a possibility...and airlines work on the assumption that if something can go wrong, it will. If one tiny Wifi interference would bring down a plane you wouldn't be able to use them...They just don't let you use them because it's unnessecary...I'm sure if you used your phone on a plane it would be ok, but if everybody did it...it wouldn't exactly do the plane any good...
Whereas if people tamper with liquids, it WILL bring down the plane.
...I used my psp on a plane recently, just don't use wifi.