How Secure are the Products of the IT Security Industry?

In the last months quite a long list of critical vulnerabilities in security products have been made public, for example in products by  FireEye, Kaspersky Lab, McAfee, Sophos, Symantec, Trend Micro etc. Wired just published this article with further information and some comments. These incidents make me think if writing secure code is just too difficult for anyone, or if there is something fundamentally wrong in how the IT industry in general and the IT Security industry in particular, is setup.