http://resourceinsights.blogspot.com/2011/02/week-of-game-changer-in-oil-or-was-it.html

Footnote:
Mark Twain: "A Gold Mine Is A Hole In The Ground With A Liar At The Top And A Fool At The Bottom"

One thing is for sure, no matter how much is really left, in the forms of unconventionals,  technological innovation will surely make best estimates liberal....JMHO