James Enck has a few posts on the subject of Skype penetration and one's rather interesting.
I actually think some telco people may really have issues with what the numbers are showing, because the adoption rate is going to impact the carriers in a few ways.
1. There will be more broadband installed
2. Cellular traffic will drop
3. Landline long-distance between family members who are all on line will drop.
As James said, "houston, we have a problem."