Nice chart P, seems to be missing a couple of labels though, the one that notes the beginning of OPEC back in 60-something? You remember OPEC, it was the group of producers who conspired to fix the price of oil and did (more or less) for 50-something years? Up til last november when perhaps they they threw in the towel because they had run out of ammo and were all producing flat out.
It doesn't say anything about the Texas Railroad Commission either, which was OPEC before OPEC was cool. The TRC essentially fixed oil prices for 30 or 40 years prior to OPEC, the same way OPEC did, by setting production quotas in the world's largest producing region. It ran out of power when demand outstripped supply at the US peak in '70-ish.
And that last big spike? No note there either but it corresponds to the spike in unregulated international speculation in crude oil derivatives and ETFs on the NYMEX and ICE. Non-participant speculation really got rolling around 1999, but was distracted by the fleecing to be done on mortgage "securities" but a few years later when speculators abandoned the real estate market en mass they were able to speculate in oil futures big time and they ran them up in a huge bubble like too much money always does. Google London Loophole and Enron Exemption, they allowed speculators who neither produce nor consume the oil they trade to have unlimited positions using the International Commodities Exchange out of London.
Not so coincidentally, in in 2007 rumbles started to be heard and futures stared to fall and by June of 2008 the CFTC had closed the loophole, speculators were locked out of the NY market, and the price of oil tanked. They were still allowed to trade the Brent market tho... and again not so surprisingly, the spread has been evident between WTI and Brent since. Here is a picture of the number of contracts:

The unregulated derivatives market (that is just betting with no actual oil ever changing hads) obviously influences the actual futures market, after all they are betting on the same thing. The futures markets themselves were invented for producers and consumers to exchange actual commodities using bona fide contracts to buy physical oil. If a producer sells a contract to deliver oil in 6 months for x dollars, someone is buying that oil, for that price and better have a place to put it. The contract may change hands any number of times spreading the gains or losses around but bottom line, the producer sold oil for the contract amount. If the price is inflated by speculation he gets an inflated price.
I posted an article recently that reported 60% of fracker's profits in the first quarter were from futures contracts. IOW, a year ago, say, those producers sold contracts for oil at $100/bbl to be delivered in February. They got real money, $100/bbl, because that was what the futures market price was at the time. Somebody bought that contract and in February somebody took delivery of that oil, real oil, sold at $100/bbl, delivered in a $50 spot market. Whether the person who actually took delivery of that oil paid $100/bbl is neither here nor there, the producer recieved $100/bbl.
The thing that is common to both the '70s spike and the '00 spike is tight spare capacity in the major producer. Kind of hard to corner a market when producers have oil coming out of their ears and will undercut each other just to make the rent—as is the case right this second. Dismissing the fairly obvious role of excess speculation because a person is afraid it undercuts their hobby horse (in this case 2005 peak oil) is bumper sticker thinking, trying to fit catchy line to a cat picture. Big price swings don't happen in a well supplied, orderly market. They only happen in one where supplies are tight and the market is opaque. Excessive speculation doesn't cover or mask the supply situation, it magnifies it.
but I'm no expert.
The legitimate object of government, is to do for a community of people, whatever they need to have done, but can not do, at all, or can not, so well do, for themselves -- in their separate, and individual capacities.
-- Abraham Lincoln, Fragment on Government (July 1, 1854)