I’ve heard examples of it happening, but can not point to any. I know my cousin was sued for changing employers, they tried to block her taking a job at a competitor(broad use of the term, but I guess fang’s think everyone is a competitor), but lost in Delaware court. So I do know they will attempt to enforce these contracts if they want to.

Many top companies do have these clauses, I’ve signed them and seen others. How enforceable they are, I’m not sure, but billionaires with armies of bored lawyers, don’t make for great opponents in legal battles.