First off, I agree that, in principle, a backdoor is a backdoor, and vulnerable is vulnerable, period. However, there's A5/3 weak, where everyone can hack it, and there's Dual_EC_DRBG, where the right secret is necessary.

What was interesting about Dual_EC_DRBG was that the default points served as sort of a secret master key to generator state leakage. It was harder than usual for another party to gain illicit access, leaving the vulnerability largely in the hands of the NSA.

It was some pretty interesting math, harder for unintended (by the NSA) people to take advantage of, and still, of course, a crippling vulnerability.

At this point, I'd be hard pressed to trust the NSA with anything security related, as they have demonstrated different priorities.

How was it demonstrated not to be secure?