Why is Insider Trading Illegal?
I'm surprised at the tone of the answers to this question! Trading with insider information is corruption and encourages fraud. As in many areas, there's an ethical line where behavior the gap between "ok" and "illegal" or unethical is thin. The classic local government insider information example is when the local councilman finds out that a highway exit is being constructed in an area that consists mostly of farmland. Knowing this, he buys out the farmers at what they think is a premium, and turns around for 10x profit a few months later. In that context, do you think that the councilman acting on that insider information is committing a crime or ethical lapse? Most people say yes.  Even in this case, the line is thin. If the same councilman has his finger on the pulse of growth patterns in the area, and realizes that the terrain makes a certain area a prime candiate for a highway and exit, buying up land would not be criminal -- but it would be risky as it creates a perception that he is abusing his position.