Sounds like he is yet to be shocked to discover why Skype is free :)
On a more serious note, Adobe Flash Player 10 comes equipped with P2P streaming meshwork, which is enabled by default and which will cause the exact same bandwidth bleed as described in article. Being behind NAT or a firewall is not enough to prevent one from being a relay node as it includes fairly sophisticated NAT traversal logic and NAT-to-NAT connectivity stuff. The only way to NOT donate bandwidth with FP10 is to disable "peer assisted networking" in Flash Settings, which in itself is done by loading a Flash applet from Adobe's site. This also makes using FlashBlock in a browser pretty much a must have.
All the calls are P2P, and if the peers cannot connect directly, the calls are routed through someone else's computer that's called a supernode. Pretty much none of the actual VoIP traffic touches Skype's servers.