mainline kernel can largely be attributed to the United State's National Security Agency (NSA). More organizations contributing to open-source isn't bad -- government or not -- when it's mutually beneficial work with good intentions. However, there are new allegations being made today about OpenBSD's networking stack, in particular it's IPsec code. The FBI allegedly paid OpenBSD developers to insert back-doors into the code-base.
Article:
http://www.phoronix.com/scan.php?page=news_item&px=ODkxMwI'm not even quite sure what to say about that..