why i resisted facebook, the long story

I just learned not to be so cavalier with the feelings of people who mean me no harm.

So, instead, a logic puzzle: one hundred engineers are in prison. They are going to be executed the next day. The executioner will line them up in a column, each engineer facing the back of the head of the engineer in front of him. The executioner will put either red hats or blue hats on all of the engineers, but who gets what color hat will not be determined until the day of the execution. The executioner will begin at the back of the line, and ask that engineer what color hat he is wearing. If the engineer guesses correctly, then his life will be spared. If he guesses incorrectly, he will be killed. The only things the engineer may say are either "Blue" or "Red"; no other words may cross his lips. The engineers meet the night before to strategize about how to save the most lives, but because the prison is a panopticon, the executioner can hear what the strategy is ahead of time and alter his plans to thwart it - for example, if the engineers all agree to say "Blue," then the executioner will put only red hats on their heads. What is the maximum number of engineers that can be saved? (Hints: the answer is a code, many more than half can be saved, and engineers can be martyrs too.)