Skype talks about monetization:
"The company does not earn any money right now, but is betting that consumers will eventually pay for premium services, like voice mail. This winter, Skype plans to introduce a feature that will enable users to call people on regular telephones - for a fee it says will be 'substantially lower'' than current phone service".
Nice one. It's tough to beat a strategy based around complementarity with durable goods people have a massive investment in already. It's also tough to outstrategize people who enjoy doing something disruptive because they believe it's good - like the guys behind Skype.
Apparently, they've already had more than a million downloads.
Small print: I made a mistake last week when I conflated Sharman and Skype - these guys sold Kazaa to Sharman, but it's not clear who own Skype (beyond the cryptic Skyper Limited).