A most disquieting idea has found me.
Humor me for a moment and assume that the world's governments are covering up an alien presence of some sort.
What if the secret they're keeping is that something hostile is coming and we're just doomed?
That knowledge in and of itself could potentially destroy human civilization overnight. Hell, maybe that's the alien strategy: Just engrave "you're fucked" on a space toaster, throw it at us and wait for the problem to solve itself.
Oh god, I'm making too much sense.