1. Make the laws on government bidding so complex that very few CAN understand them. Requires power.
2. Grease the skids to overcome the inevitable subjectivity inherent with people trying to interpret complex rules (crony capitalism). Requires money.
3. Shazam! You win the bidding process.
While there could be a backdoor, a more rationale conclusion is the involvement of these government agencies is to help insure the O/S has the capability to be highly securable. Very few programmers outside of government have the same security worldview as the NSA/DoD, so MS needs that government expertise to assist them. http://iase.disa.mil/stigs/index.html
And America is NOT spying on China?
Current U.S. law prohibits cyber attacks against systems in other nation-states.
I doubt Symantec's warning was geared to a Slashdot audience, but towards those Neanderthal carbon interface devices that refuse to pay for an AV service or application. Usually, I just want to slap users (twice) and then ask what problem their having with their system. MS didn't develop free AV software to compete with other AV companies, but to protect their OS against negligent, recalcitrant, cheapskate, or just plain ignorant users.
It can also be said the AV manufactures over-priced their products, putting AV protection out-of-reach for some, regardless of their intellect.
Overdrawn? But I still have checks left!