Reuters has extracted a few more stats from Skype during an interview with the co-founder. According to Janus Friis, Skype's users are "...44 percent in Europe, 29 percent in Asia, 13 percent in North America and 10 percent in South America." Skype users by country are here.
Friis also said "We're investing heavily in our infrastructure", which is a bit contrary to the line they have run in the past about very low costs. We know Google is investing in infrastructure, such as dark fibre, but Skype "investing heavily" in infrastructure would be a new turn.
