Go ahead and read Skype flaws open computers to attack:

Skype Technologies updated its popular Skype Internet telephony software on Tuesday to fix a pair of security bugs. The most serious flaw could allow an attacker to commandeer a user's PC. That flaw, which is similar to a bug Skype fixed last year, affects only Skype for Windows. An attacker could exploit the flaw by crafting a special link and enticing a user to click on it. The flaw could also be exploited when importing user information from a malformed electronic business card, or VCARD, Skype said in an advisory.

I got one word for ya: DUH! Skype already boasts how many millions of users (of which, I am one). How many more users will it sew together when eBay starts actively pushing it forward? The malware writers are going to have a field day with this one (trojans, worms, and virii – oh my). Skype trounced the competition because it was based on a P2P archetecture and infrastructure. It's greatest strength will also prove to be its greatest weakness. Favored child or not, Skype may very well become the “Internet Explorer” of the IM world. I personally don't run Skype unless I need to – largely because (to my knowledge) Skype uses Internet bandwidth even when I'm not inside of a call (which is a feature, not a bug).