Why is it always a conspiracy? Flip a quarter 100 million times, you'll eventually get heads 100 times in a row. Now flaw in the quarter, just as it's not a flaw that a few blocks get solved in a short period.
You need some serious probability classes around here. No offense please...it is a joke...
If you flip a quarter 100 million times and the probability of getting sometime 100 times heads in a row is 10^8 / 2^100 x(10^8-100) =7.8 10^{-15} pretty small
In order to get heads 100 times in a row you need to flip your quarter about 10^22 times...my guess is that your quarter will disintegrate in the process...
It's slightly more complicated as it involves Bayesian probability although you're close. A run of 20 heads is a roughly 1 in a million occurrence and the required rolls goes up exponentially the higher you get. For more information, see:
http://www.drdobbs.com/architecture-and-design/20-heads-in-a-row-what-are-the-odds/229300217