What I've realized is that the things I thought were paranoid and came true are things that I thought were paranoid because I had "trust" in various organizations not to abuse power, not because the actions seemed out right implausible.
With the backpacks and pressure cookers story, I was skeptical not because I trusted the fbi, but because it seemed implausible given the way the fbi typically acts and strongly against their interests.
So my updated rule is that 'trust' is no longer a valid reason to rule something out as paranoid. This is an ethos that the security world has long held as obvious, that many technical people formerly not particularly interested in security are waking up to.