http://answers.onstartups.com/questions/19422/if-im-working-...
"Not related to your employer's line of work. Um, wait. What's the definition of related? If my employer is Microsoft, they do everything. They made a goddamn BARNEY PLUSH TOY with a computer in it once. Are plush toys related? Obviously operating systems, compilers, desktop applications, search engines, and games are related to Microsoft's line of work. Hmmm."
"This ambiguity is meant to create enough of a chilling effect on the employee working in their spare time that for all intents and purposes it achieves the effect that the employer wants: the employee doesn't bother doing any side projects that might turn into a business some day, and the employer gets a nice, refreshed employee coming to work in the morning after spending the previous evening watching TV."