If the target were being investigated for terrorism, then the govt could inform the company of that and - if the company tipped the terrorist off - prosecute the company for being an accessory / aid to the terrorist.
However, if the govt claimed that the person was a terrorist and the company knew for 100% fact that the person was innocent and the investigation was in bad faith... they could tip off the victim.
The NSLs only really help in the latter scenario. As long as the govt has a plausible story, there will be a 50% chance that the target is a criminal and the company will not risk notifying the target. With NSLs they can prosecute the company even though there was no legitimate basis for the investigation and everyone knew it.
> govt claimed that the person was a terrorist and the company knew for 100% fact that the person was innocent and the investigation was in bad faith...
This is the thing tearing at the seams of our justice system in general. Our rules are based around an ostensible checks-and-balances arrangement, but this relies on the assumption of good faith from the parties involved. Implicit in this is the idea that if any body isn't acting in good faith, it will be so repugnant to voters that the state of affairs will quickly come to an end. This assumption is false.
Now we're talking about granting Facebook the right to assume bad faith on the part of the FBI!? Like granting the power to ignore the government to private companies will solve this, or help at all? That bandaid solution is almost certainly worse than the disease.
That's not to say that I agree with secret spying provisions. They clearly violate the Constitution and undermine trust in democracy. I just don't think "if you're a big enough company you get to ignore orders and drag things out in court" is a solution to government overreach. It's individual rights that need protecting, not corporate ones.