EROEI exactly
Exactly. EROEI is the key.
Please look it up: http://en.wikipedia.org/wiki/Energy_returned_on_energy_invested
Ask yourself why don't our cars run on (renewable!) whale blubber diesel? There are still whales about, you know, just ask the Japanese who "research" them.
The answer is because petroleum-based fuel was cheaper during the 20th century and still is at the moment.
Rudolf Diesel would have understood EROEI.
The two examples you mention, hydraulic fracking and synthetic fuel, have drawbacks which is the reason why they are not used currently: both are bad for the environment and the EROEI is really quite a lot lower than other current fuel production methods (e.g. South Africa Sasol's Fischer-Tropsch synfuel: google it).
You mentioned that there are hundreds of new wells in the USA to extract their huge amount of shale oil with hydraulic fracking. To me this doesn't sound like a brave new world of cheap fuel, but as an act of desperation to keep continuing with the profitable status quo for a little bit longer.
You cannot in the 21st century decouple the inventivity needed to get resources from the *energy investment* needed to get those resources otherwise you will fail.
Also, in economic terms the discussion often focuses on our "need" for fuel and energy. But unfortunately, physical rather than economical reality doesn't give a hoot about our "needs".
To put it differently, thermodynamics trumps economics. We're finding that out now.
I'll end my long and no doubt tedious rant by stating that I, a "tree-hugging hippy" as you'd probably call it, *love* human ingenuity and innovation and I sincerely believe that in 100 years we will still have wind and sunlight to our disposal to provide energy and food (lookup energy costs of Haber-Bosch process: http://en.wikipedia.org/wiki/Haber_process ) for whatever size world population that can fit within those energy constraints post-Peak Oil.