I was booted from a group once, by the DM, in a very roundabout fashion.
It was a big, dramatic, political/intrigue campaign, and it was the first time I'd played in a campaign where the PC's weren't all allies trying to help each other, which was a big adjusment to be sure, and since I'd joined the campaign in-progress I was walking into a political minefield of established friendships and rivalries, it's not long before I've accidentally burned some important bridges and gotten myself honor-bound and indebted to another PC as a virtual slave because I didn't understand the many intricacies of the setting.
The DM sets up a big "special" session, where plotlines from the last 6 months or so are coming to fruition, and the DM says to underscore how important this session is, anybody who dies who has a character die in this session is out of the campaign, ressurection magic not existing in the setting.
I manage to survive some truly heinous fights with CR's way over my head, work my way out of some fierce traps, and survive what was a pretty killer adventure. Then, after the climax and as the game is winding down, we're back in town and wrapping up when the DM asks for a fortitude save out of nowwhere. I roll a 22, which apparently wasn't enough. He then gives me a flashback to a day before, when an NPC handed me a tool I needed while bypassing a trap earlier, and I now realize the tool was coated in contact poison, with no initial damage and a 1-day secondary damage delay. The save DC was over 22, it was Constitution damage poison, and my 11 Con character was killed outright by the secondary damage (he didn't even roll the damage, when I pointed that out, he said he'd rolled it earlier), so my character was killed. As a sort of consolation prize, he underwent divine ascention to being essentially a demigod, but I was out of the campaign, and as soon as he died, the session ended.
He never admitted it, but I always interpreted it as being booted out of a campaign.