Since it takes some time to determine whether someone has gone overboard on conspiratorial theories, I have a quick test which gives immediate results. First, find the theorist's website. Then look for HTML background that looks like this texture:
I guarantee it will accurately predict tin-foil at least 99% of the time. Find a textured home page and you will find tin-foil-hat-wearers lurking nearby. Let me test my theory:
Another 9/11 textured page:
And one more on an unrelated but even more insane topic:
Why do the conspiratorially inclined go for this background texture? Occam would explain it as old farts never updating their pages beyond HTML styles circa-1996. I would prefer to think of it as an subconscious plea to shadow whatever they say with crumbled tin foil:
Yet, I still don't quite understand why WTC building #7 went down.