In the movie "Wall Street" (1987) Gordon Gecko has his lackey Bud Fox follow a rival around to try and figure out what he's going to invest in, so they can undercut him.

He follows him to a private jet and finds out it's flying to mid-sized city that happens to be the corporate headquarters of a particular company. In the movie it's sort of implied that this activity is illegal.

I wonder if it actually was, and if so, why that would be different than what those hedge fund guys you reference were doing?