I don't remember the source, so I might be making this up, I kind of remember Bill Gates stating that they would rather hire someone and keep them busy as letting them work for the competition.
I have a similar vague memory. That being said, that also works as a pretty good post hoc justification for having some guys randomly doing research and not really delivering what you hoped they'd deliver ("Hey, at least they didn't go off and make another Microsoft!").
