As in all things, it depends on your perception of "safe".
I just took a network analysis class where we did a bit of in-depth talking about Skype. One of the interesting things to note is that it was developed by the same folks that brought Kazaa peer-to-peer music file sharing. Once they got smacked by the RIAA, they decided to "enhance" the same technology and use it for voice and video peer-to-peer connections.
Some things to note: Although the voice and video traffic is encrypted from end-to-end and does a "port hopping" algorithm (makes it harder to firewall it), your particular Skype session may traverse two to four computers between your source and destination. Skype makes use of "SuperNodes" to route traffic through the peer-to-peer cloud. Not that it is a bad thing, it just means you should be aware of it.
Two things to do with Skype - Never accept an unkown solicitation to connect (like never open an attachment from someone you don't know). and Two, go into the advanced properties and uncheck the port 80 and 443 connection option. This will prevent you from being a supernode if you are a heavy Skype user and have a high bandwith, unfirewalled connection to the Internet.
Use at your own risk.
Oh yeah - PC -would you PLEASE turn off your webcam!!!! I don't want to see ANY part of your naked body... (hint: Christmas pics - lol)