I had some friends who were fully sold on Peak Oil for a few years. Basically: we were about to hit the point where supply of oil was going to fall below demand once and for all, and there was no viable replacement, so prices were going to skyrocket, societies would grind to a halt, wars would start over the dwindling oil resources, and we were going to be living in a post-apocalyptic wasteland within 10 years.
In ~2009, the price of oil hit a record high of nearly $200/barrel. This was at the tail end of a sharp jump, after 20 years of steadily-rising oil prices. One of my friends was pretty obsessed, and had been reading blogs and listening to podcasts, and had all kinds of facts & figures on oil production, known reserves, predicted demand, etc, and they all seemed to point to a crisis. He predicted a price of $300 or higher per barrel within a year, and that was just the beginning.
So we made a bet on where oil prices were going to be in 5 years. He said (with absolute confidence) $300+, I said somewhere under the current price of $200.
It ended up being under $100/barrel. Nobody talks about "Peak Oil" anymore.
(I won't say where I got my confidence that oil prices would stabilize and fall, because that would just invite a barrage of downvotes and angry arguments...)