Perhaps the better term would be "Skype-osphere" - the evolving universe of equipment and applications developers building on interesting ways to extend Skype usability. Case in point -the UK's Connectotel today launches a public beta of Skype-to-SMS. They were kind enough to make me part of the closed trial, and it worked like a charm. Particularly for the youth segment, this fits in a very sweet spot between two highly addictive behaviors, SMS and IM, and will also save them money.
SMS isn't chump change for the operators, either. In Q3 last year, UK cellular users sent 6.3bn SMS/MMS (I'm sure most of this was SMS, and the figure doesn't actually include Virgin Mobile), and SMS/MMS operator revenues were GBP508m, or 17% of total turnover. I calculate that in Q3, UK cellular subs sent 1.2 SMS/MMS per day on average.