Yes, how dare they put ads on their free service used by millions. After all, developing software, providing server maintenance and bandwidth costs nothing to them.
It's not just that. There's a lot to say about advertising, but ads have a history of starting off innocent, but end up becoming intrusive and obstructive. Take a look at a typical webpage with AdBlock turned off, especially one running Google's ad network. You have ads all over that it becomes intrusive to user's browsing experience. It didn't used to be that way, but slowly, over time, they've crept up on us.
Now, they're placing ads in our software. Software many live or die by, that to me is unacceptable. I don't need ads junking up my desktop UX. I know developers need to eat too, but in software advertising isn't the way to go. I don't trust ad networks, I don't want to be tracked, or cataloged. I don't know what that little ad is doing behind the scenes, or what kind of data it's sending back home. We have a word for that in the business, that's called
adware, and adware is generally frowned upon nowadays.
I installed Skype to talk to people, not be followed around by a sleazy used car salesman.