It was and because of that a lot of people were hacked, since skype could be used to run remote code by leveraging a couple of bugs existed in skype application.
That is one of two reasons why Microsoft switched to server-client model instead of p2p connection.
Other being having control of the service and with call and message history makes more money of course.
That is an interesting perception of history. What it looked like legally was p2p was working great and skype was massively rising in popularity. But the US federal government could not stand encrypted peer to peer communications. So they told their good friends over at eBay to buy the company. eBay messed it up and only bought the license for the name and not the actual code and p2p backend. Things continued working well for a while. But the feds still weren't happy. So they had their other friends at Microsoft actually purchase the technology and then immediately destroy it and switch to a centralized model.
>For the second time, Zennström and Friis cashed in on selling Skype. That's because, instead of giving eBay the critical base technology that kept Skype going (the P2P system known as "Global Index"), Zennström's and Friis's company Joltid still owned it—they simply licensed it to Skype. The whole situation devolved into threats of litigation until a 2009 settlement gave Zennström and Friis a chunk of Skype ownership, which made them even more money when Microsoft bought the company.
That is one of two reasons why Microsoft switched to server-client model instead of p2p connection.
Other being having control of the service and with call and message history makes more money of course.