I am writing this from about the great State of Arkansas on my return from Dallas. After we took off I immediately jumped on my iPad to make the most of my time and get some work done. I connected the wireless and opened my browser to pay the exorbitant fee for internet ($12 for 90 minutes). My browser launched www.google.com and I was able to see the search engine page like normal...but I didn't log in or pay. So my wife and I poked around it a bit and it turns out we were able to search in Google, view images, and a number of other things...all for free on Google. Now I understand the ability to surf on US Air's website for free. But Google? Lot's of stuff to do there.
This is a prime example of a small hole that will no doubt get abused. I wasn't looking for it, but I found it. Imagine if I spent the rest of the flight finding other holes in the system?
You can never test your system enough. And by test I don't mean test to see if it works, I mean test to make sure things don't. Testing for failure is as important as making sure what you want to work does.