It's a fairly specific term so trotting it out for everything makes it pointless and obscures its actual meaning. Every time someone misunderstands something about information security (or someone thinks they do), someone else comes along and says 'Security through obscurity!' or 'Trusting trust!' or something about source code. It turns these things from terminology and concepts into magical-sounding incantations that really just mean 'I disagree/don't like this'.

This is analogous to the more familiar overuse of 'ad hominem' and 'straw man' and so on. It's not a good thing.