When I was at MSFT a little over 10 years ago the norm was that to be that if you gave notice, and said where you were going, and it was a competitor in certain industries, you would be escorted out immediately or same-day.

Our extended team was pretty collegial about this -- de facto, people could choose to work out their 2 weeks by keeping quiet, or to leave right away by naming a name. (I think this got you some extra vacation? Never quite sure how that worked out.)