In the not-too-distant past, I had the misfortune of being around probability trolls. Those who would exploit the bugs in the definition of probability to produce ridiculous answers to fermi-type problems.
Q. What is the probability that there is life on Uranus?
A. 0.5 – either there is life or there isn’t.
Q. What is the probability that the earth will be destroyed because of the LHC?
A. 0.5 – either it will be destroyed or it won’t.
And so on.
The source of this trolling is contained in the naive definition of probability :
P(A) = |E(A)|/|S|
And it pisses me off. But I guess that means that the troll’s mission has been accomplished.