(1) Microsoft is a US Corporation
(2) With the Skype acquisition, Microsoft (arguably) becomes a telecommunications carrier.
(3) CALEA passed in 1994, "requiring telecommunications carriers and manufacturers of telecommunications equipment modify and design their equipment, facilities, and services to ensure they have built-in surveillance capabilities, allowing federal agencies to monitor all telephone, broadband internet, and VoIP traffic in real-time." [a]
My (unfounded, optimistic) speculation is the skype acquisition was strategic positioning in the mobile market: seamless cutover to skype when your phone has WiFi.
a - http://en.wikipedia.org/wiki/Communications_Assistance_for_L...