There have been conspiracy theorists as long as there have been conspiracies, i.e. pretty much forever. Do conspiracies exist? Of course; without them politics and politicians would probably cease to exist (can there be any more damning argument against conspiracies?). Where the serious conspiracy theorists go wildly off-beam, though, is believing that because conspiracies exist and because politicians will use anything and everything possible to further their own objectives this means that everything that happens everywhere is part of a covert, fiendishly cunning globally coordinated conspiracy, usually involving Jews, Al Qaeda, the Illuminati, lizard people, Freemasons, the Bilderberg Group and/or the CIA, that only the theorists are wise enough to see.
In Conspiracy Theory World there is and can be no such thing as coincidence; if the neighbours start putting their rubbish out ten minutes earlier, it's proof that their CIA handlers have ordered them to do so in order to catch the heroic guardians of truth off-guard prior to marching them off to FEMA camps (or just prisons in the UK - these austerity cuts are leading to all sorts of cutbacks). Massive narcissism is, after all, a defining characteristic of conspiracy theorists, who like to believe that their rantings in the windier corners of the internet are causing sleepless nights for spies everywhere. If this were true, of course, it would be a great comfort to know that the world's intelligence services have nothing better or more dastardly to do than monitor people who last made contact with reality and soap in their schooldays.
In ancient history before computer ownership was widespread (i.e. over 15 years ago), the conspiracy theorists had a harder time of it; they had to share their, ah, interesting theories on our lizard overlords/the New World Order/the Jewish world domination plot etc with those around them, who would mostly back away fast muttering "Really, how fascinating…is that the time? Must dash", or via letters to the papers. Sadly, of course the newspaper editors generally proved themselves to be media lapdogs and co-conspirators with The Massive Global Plot by not printing these revelations; sure, they may have claimed that they didn't want to give space to the tragic dementia babble of disturbed minds, but uh-uh, the letters' authors knew the real reason; their uncovering of the truth was just too much for the Establishment to take.
The advent of the worldwide web, however, was like all the theorists' Christmases come at once; suddenly there was a global forum where they could connect with like-minded paranoid, socially inept loners who also saw The Big Picture and knew what was really going on. Oh sure, the foolish sheeple - the rest of us - still couldn't or wouldn't see the truth, but the brave warriors for truth who turned down the red pill (The Matrix series is conspiracists' cinematic nirvana) could no longer be silenced by The Man and would henceforth share their insights into global geopolitics at every and any opportunity. And boy, have they shared.
This heartwarming generosity would be fine if they'd just limit themselves to conspiracy theory sites and chatrooms where they could endlessly exchange their vast knowledge and insight into the Illuminati, the Papal Nobility from Ptolemaic Egypt who control the Vatican and the world, (although they're presumably competing with the Jews and the lizard people) and pretty much everything else. Everyone needs a hobby, after all, and if the stupid can have their own websites (welcome to Paris Hilton.com), I don't see why the deranged shouldn't have theirs too. Voltaire nailed it a few centuries back; although I probably wouldn't fight to the death for them (I might throw a small rock, but let's not get carried away here), they deserve the same freedom of speech as everyone else.
Unfortunately, however, the theorists won't respect the rights of we sheeple to be left to our contented ovine existence online. In any chat room, on any newspaper comment thread, you'll find them cackling at the blind sheeple who believe that Bashar Assad or Kim Jong Un and their predecessors aren't heroic leaders, that freedom's actually not a bad thing to want, or even that there are maybe some good points about living in Western democracies, however imperfect they may be (like, oh, the failure to jail conspiracy theorists). And with global economic turbulence and mainstream political parties becoming ever more interchangeable, the theorists' dribblings can be more attractive than they'd otherwise be to desperate, disenchanted and naive people searching for some unifying theory to make some sense of an insane world - and we've been here before.
As in the 1930s, therefore, this is a period when the extremists on all sides come into their own, and the conspiracy theorists, more especially those who have a handy scapegoat to pin the world's problems on (Jews being the trustiest standby, although Muslims are fast catching up), are nothing if not extreme. So while their dementia babble may be mildly amusing in a contemporary Bedlam tour sort of way, we really shouldn't take the conspiracy theorists as a harmless joke; as Europe found out to its massive and tragic cost previously, when enough people fall for toxic nonsensical drivel, it really isn't funny - or harmless - at all.