A concrete example. I was courted by a company a couple of years ago to join their engineering team and I was pretty set on joining the company until I spoke with a former employee who told me that this company had reneged on giving him the option to purchase his ISOs because they didn't like that he was leaving after two years.
That's completely unacceptable behavior for a company, and it completely changed the way I look at equity. A company can't come at for my already-cashed paychecks, but they can absolutely prevent me from purchasing my options for pretty much any reason.
(1) https://www.mystockoptions.com/content/how-does-a-clawback-w...
As a single datapoint, I was in the final stages of interviews a while back. I had a call with the CEO where we got into some details about company funding, equity compensation, etc. When I pressed him on the 90 day exercise window he acknowledged their VCs liked it that way because it meant options flowed back into the pool when folks couldn't afford to exercise. I adjusted my salary numbers accordingly and we were unable to find common ground.
No, I don't feel like naming and shaming.