Well, I've had two or three "booted" characters, but the thing is, I'm friends with two of the three still. And I don't think any of them ever felt like they were "booted"
The first was a guy who would often not show up. He loved playing, he was immersed when he got there, and all that. Now, some of the other players made fun of him a bit, but that's my group - we tease each other, constantly. And he just never fought back. Turns out he was (is) suffering from depression, which was why he'd miss games. I wound up telling him "I'm not comfortable with you using the games as a vehicle for you dealing with outside problems. If you can't make regular apperances, it screws things up for everyone. The table's always open to you, once you can make the regular session time, but right now, your absences are hurting the entire party." He left on good terms, never came back. And, to the best of my knowledge, still hasn't taken any steps to deal with his depression.
Second was similar to the first - a guy that would drop in, play a few sessions, and then leave with no explanation. And then do it again. Usually, I'd have no idea he was gonna show up until he was there, rolling up a PC. His brother (a regular at my table) would just invite him, knowing I liked him. But it was a pain in the butt to just deal with. I finally just said "hey, if you can't make it every session, could you not show up? It's sort of a strain on everyone else". The guy hated 4e anyway, so it worked out well. He sometimes talks about joining the next campaign I run that isn't 4e, which sounds good. he's a fun player.
Finally, there was a guy who joined our Savage Tide campaign. Had fun, although he was a "voice actor" whereas the rest of the table generally prefers third person communication with NPCs. Our general attitudes - and the fact that we were a more beer and pretzels game and less focused on the fantasy world than he preferred - convinced him to leave. Which was fine, because I was getting annoyed with his fake flirting with my girlfriend at the time. And then, after the girlfriend and I broke up, I found him sending him all sorts of messages on facebook (he was supposedly my friend, and that's just bad "bro code"). He doesn't know it, but he's not allowed back at my table.