Please understand also that my previous post was not intended to be cynical. Skype does use commercial-grade encryption to protect the message traffic from "casual eavesdroppers," as it of course should do. Just bear in mind that what they are defending against is "the nosy next-door neighbor on the ultimate world-wide party line," not any government agency in the world with a three-letter acronym. Like every other commercial-grade encryption system in common use on the internet (say, https://), it is quite stout and effective against its intended opponent.

And I would still use the service with the same set of guiding assumptions that you might use, say, with your telephone ... ... despite everything that encryption and so-on might do, you should presume that every scrap of anything you do or say is being recorded.

(And, most likely, subjected to the treatment illustrated in the movies. Your Government Servants At Work ... yep, they're the same the world over, and face it, whatever you might have to say isn't actually interesting to anyone anyway. )