I can't help but notice the exact wording of FB's response - or rather what they didn't say.

If someone asks me to do them a favor, I have basically three options for a reply:

• I can and I will;

• I can but I won't; or

• I am not able to.

FB's answer was not option 3.

I think a more plausible explanation is that FB did not want to set a precedent of being the facial recog avenue of choice for the Fed.