The heavy stuff and the rest become more economical to extract and refine, and a new far higher finite supply is realized almost magically.

Classic argument that I have seen 100s of times on the web. Nobody he's questionning how large the tar sands can be. The real question behind PO he's how fast can we convert tar sands to synfuel. Here is the mistake: PO is not about How much oil is left but, I quote Colin Campbell:

What is Peak Oil?
"The term Peak Oil refers the maximum rate of the production of oil in any area under consideration, recognising that it is a finite natural resource, subject to depletion."
Oups! sorry for the typos, I hit the post button instead of preview!

Notice that people pushing the tar sands/shale oil argument never adressed the question of what will be the production rate from such sources.

Because if they did, and were honest about it, investors and the public at large would be appalled and say "Wait? That low?!?"
Maybe we should rename "PO"
as "PoW-Wo-ER":

Peak of World Wide oil Extraction Rate


(Painting: Morning Pow Wow --err)