Review: Assessing Skype's network impact
New independent review on Skype's security on corporate networks.
"Our testing shows that neither Skype VoIP nor Skype Instant Messaging poses any readily exploitable security threat. We also conducted a dozen private interviews with hackers, enterprise network managers and leading network-security-equipment suppliers, none of which could cite one case of Skype being exploited for insidious security assaults."
For more info see http://www.skype.com/security