It seems to me that a warrant canary being updated after public notice is the most definitive proof we have that Silent Circle hasn't been served with an NSL.

It seems to me that a warrant canary being updated after public notice is the most definitive proof we have that Silent Circle hasn't been served with an NSL. If the NSL had the ability to force an update, the canary would have been updated before anyone noticed it was a problem. If the NSL didn't have the ability to force an update, the canary would still remain un-updated.