Phil Wolff at Skype Journal points out a rather amusing fact: in order for authorities to snoop on Skype calls, spyware has to be installed on the Skype PC. The scary thing? There's a legitimate company trying to sell a tool to do exactly this.

Once you've infected the endpoint with this tool, you've not only got access to everything Skype does, but just about everything else "encrypted" on the computer, too. As far as I'm concerned, you could use the same hack to "listen in" on VoIP calls with just about any VoIP soft client out there. In all honesty, you might have better luck doing that versus trying to tap the network and listen there.