I like the idea, but I don't like your system of using extrapolatedpredictions. I say you let people do something like make up to 4predictions for each match, depending on who the entrants are. Forexample, if the first round matches are A vs. B and C vs. D, then forround 2, a prediction would be something like

If A vs. C, A with 60%
If A vs. D, A with 58%
If B vs. C, B with 51%
If B vs. D., D with 50.2%

Ofcourse, for later rounds, this could get out of hand, so there wouldhave to be some limit on the number of possible pairs you could predictfor. If your pair is not the actual pair, then you automatically get nopoints. I just picked 4 out of the air, maybe I slightly larger numberwould be better.
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Despite being in an 11-way tie for 4th in the Guru challenge, I got totally owned by Yoblazer.