This sounds like stealing to me. DNS/ICMP tunneling is a clever hack, but the end result is that you are using someone else's bandwidth without paying for it.
Anyone know how this compares to the instructions at dnstunnel.de, which uses ozymandns perl scripts? I've been using this method, and though it works, it is horrendously slow (takes a minute or more to load gmail...)
Once I've been using free wireless in the JFK airport. But my laptop ran out of the power. I found power socket in the floor near the phone booth, and plugged in my laptop. After some time security guy came and told me that I shouldn't do that.
So when I was passing to the plain, they looked through all stuff from my luggage. Then they apologized "for the mess"
Be wary of ad-hoc networks in airports. Ever time I've fired up a wireless device in an airport I've seen a "Free Wifi" ad-hoc network which was almost certainly some dude with a laptop trying to steal peoples data.