Wow! That's a thing? I had no idea! It makes sense, though. When you're in touch with so many people, and put in the position of saying no to such a personal aspect of life and work, there will inevitably be the few who threaten to set you on fire.
So, though I wouldn't consider it a formal one--and it contains fewer that five people--yes. All for fire-like offenses. I like myself uncooked, thank you. And wear appalling amounts of sunscreen to stay that way.
Yes. In a weird twist, I usually take longer to get back to the people I know and like.
To give you an idea of how incredibly behind I am, I haven't responded to my real-mail penpal since February. And you know how much of an advocate I am for real letters. (Really. Send them everywhere! Even a well-placed line or two can make a huge difference. I'm sure most companies assume that, for every real letter, there are ten or twenty people who have the same opinion but are too lazy to write.)
So, yes. I do have an informal blacklist of 3-5.
But, if you haven't made any flammable threats, you are not on it.