It's still speculation, and one of Skype's lead engineers wrote a completely sane explanation of how the centralization had to happen if Skype was going to work

It's still speculation, and one of Skype's lead engineers wrote a completely sane explanation of how the centralization had to happen if Skype was going to work well on mobile, since you're not exactly going to be getting tons of supernodes on iPhones. You're welcome to believe that they also did it for government reasons, but there are definitely sane technological reasons, too. I'll update this comment with a link in a few minutes if I find it.