Which is actually what Skype excels at. For $30/year I have a Skype-in US number and can make unlimited US calls. There are SIP providers that do the same thing, but Skype is #1 for consumers.
Not that I think Microsoft spent its money well. Since it's a platform developer its a conflict-of-interest for Microsoft to own Skype. This immediately devalues Skype since other companies won't want to play ball. And Skype is hardly a monopoly so other companies don't have to.