Except, in the general case, that isn't true. Many of the Park Service social media accounts that were shut down do disseminate emergency information.

That part of the "shutdown" was rolled back once the issues were understood, but in the interim those kinds of Twitter feeds were pointing people to their Facebook page for up-to-date information. I guess we're lucky that no one included Facebook in the shutdown order and even luckier that there was no relevant emergency while the social media policy was being clarified.