It signifies a set of possible statuses; more precisely, either the presence or the absence of a Blackberry actually signifies something more like a probability distribution over statuses. (More precisely still, they're likelihoods rather than probabilities, and needn't sum to 1.) The absence-of-Blackberry distribution is like a notch filter; learning that someone doesn't have one makes it (or did, a few years back) much less likely that someone occupies the middle-to-senior-manager niche.

This (I take it this is your point) can produce more counterintuitive updates than a more "unimodal" signal like the presence of a Blackberry. Learning that someone has no Blackberry will tend to make your assessment of their ( corporate) status more "extreme". You can call that a sign flip if you like; I'm not convinced that's a helpful way to look at it.