Ask HN: Know anyone who's side project IP was legally challenged by the day job?

On this post here - https://news.ycombinator.com/item?id=20019975 - and many others like it, I've seen folks get quite worried about working on side projects while working for the man. In the comments I asked the question "Does anyone have any anecdotes about companies enforcing this rule and coming after a founder that started a side project while working for the company?" I got 16 upvotes even though the question was quite far down the page. Since I've never had that many upvotes on a question so far down I am thinking maybe other folks would be interested to hear about real world cases like this. Does it happen often? Does it ever happen? All anecdotes welcome!