"There is no physical connection between the two. Anything that needs to be done between the two networks involves your ten fingers reading output off one machine and using it as input on the other, or vice versa."
OMG, I had wireless all this time and didn't know it.
This does sort of raise the question: when Valve finally sets up the subscription model for future games and services, how secure is your subscriber info and credit card number going to be?