From Nicholas Thompson’s “Who Needs Keys?” (Legal Affairs: November/December 2004):
The event was organized by 2600, a quarterly magazine whose name refers to one of the great discoveries in hacker history: that the plastic whistles given away free in boxes of Cap’n Crunch cereal in the early 1970s could be slightly modified to create sound waves of 2600 MHz, a frequency that allowed you to make free calls on the old AT&T phone system.