Audit is always there. To be specific, OpenBSD and FreeBSD do have designated "security officers" whose job is just this. No code is committed to the source tree without them poring over it with a serious "magnifying glass". I think the problem starts when there are several security officers, who then happen to "leave the job to the other officer" or when the security officer gets compromised. Somehow, you cannot stop the FBI if they wanted something, or could you?
I see this issue as being more about FBI (I am being specific) dirty tricks and not Open Source development per se. For the coders who fell for the FBI's bait, it's simply a betrayal to the OS community and should be seen as just that.