I know what you mean, Stu.
I suspect future sociologists will find a wealth of material in the various conspiratorialists and their misguided beliefs in the 20th/early 21st centuries.
I think I would point the bulk of the blame at Vietnam and Watergate. Government - rather, the public perception of government - went from a positive view during the second world war and throughout much of the 50's to one of increasing disbelief and horror in the late 60's.
Nixon's ("I'm not a crook...") mobsterism of the early 70's led the way to Reagan, Clinton, Bush#1 and #2 all lining their own pockets (and more importantly the pockets of their friends) which just looks evil to the man in the street, whatever their political persuasions.
Where governments go, big business/organisations follow. Enron, for example. It's impossible NASA wouldn't be tarred with the same brush..."they must be somehow corrupt." Hoagland and others build on this to make a buck and feed (mislead) the public.
NASA's additionally saddled with the fact that to understand what they do (on a level beyond enjoying the amazing pictures and events) requires a scientific mind. You can't simply "feel" that a shuttle will get into orbit without some idea of delta-V, isp, exhaust velocity and the rest of it. The dumbing-down of education - and here in the UK educationalists were discussing last week to change the word "failure" to "deferred success" in classes - does NASA no good at all.
Naturally a dumbed-down public make for easier prey for the TV networks. Why broadcast, for example, a 50 minute lecture on a scientific topic when a soundbite and sensationalism will attract more viewers?
I despair.
CP Snow's concept of "Two Cultures" has never been more valid...
Andy G