I'm sure that, as with most mental illnesses, susceptibility to conspiracy theory would be a scale (say, not-very-susceptible to highly-susceptible). And in that case, we're all on the scale somewhere.

As you mention such weaknesses being "actively exploited", it makes me think of advertisements / advertising agencies attempting to manipulate people (to buy stuff, etc.). Perhaps our location on the conspiracy-theory-susceptibility scale would correspond with our susceptibility to advertising tactics, such that those who are more likely to believe in conspiracy theories correlates with those who are more likely to buy something based on seeing an advertisement. Or perhaps there's even some element of training in there, whereby some people might be "trained" by advertisements into being more likely to believe in conspiracy theories.

Or maybe I'm just trying to pin negative behavioral consequences to the advertisement industry, a facet of our society that I find loathsome.