Well, actually if he "conspired" to kill JFK there is a conspiracy ~ others must have been involved. However this isn't something that is considered true and supported by evidence as far as I am aware.

What is known is that Lee Harvey Oswald did shoot at JFK and JFK did die from gun shot wounds. It is also considered proven that LHO was the sole shooter, responsible for killing JFK. It was also a pre-planned, pre-meditated act, but unless others were involved that doesn't make it a conspiracy. (Con = with, conspiracy "to agree or plot with" ~ not something you can do alone.)

Well, you're right, that's a bad example I used.

Going back to 9/11, the hijackers conspired to do all that. A conspiracy theory might add to that: the US government plotted it or was in on it somehow. But it would be immune to any evidence which calls that explanation into question. It's not actually a theory that can be put to the test.

That's the hallmark of a good conspiracy theory - government involvement (or acquiescence, as many 9/11 conspiracy theories contend).

I find them hilarious in that the same government that can't put together a website for a healthcare exchange, keep a mid-level analyst (or a PFC in the Army) from accessing and releasing to the public huge amounts of classified material, or commit a low level burglary effectively* is somehow able to pull off these convoluted plots with perfection and no leaks.

* Good grief, G. Gordon Liddy and his intrepid band of black ops professionals was thwarted by a security guard. They duct taped a rear door to keep it from being locked from the outside twice. The first time the guard saw it he simply removed it and went on his way with a shrug. They didn't even need it there, as the door could be opened from the inside, letting them out without needing a key.

If Mr. Liddy was half as good at burglaring as he is at generating his own press they'd of gotten out scott free!

Ah, but Dart, Liddy was just the lightning rod. While he was distracting the guard with his obviously 'stupid' tactics, trained landsharks with laserbeams attached to their heads went in and planted a blue dress that was to be found 20 years later.

GPS doesn't work that way.

They absolutely do. Haven't you ever watched NCIS, 24, or any other documentary on government agencies?