This has probably been brought up but here is my opinion on why we REALLY need this:
1) You are running any quest where at some point the whole group has to be present to advance. You happen to get that person who says "Gotta go afk for awhile" and now you get to that point and he doesn't come back. You have 2 options currently...start over or wait and hope he returns. Going AFK is fine as long as you tell us how long and you don't hold the group up =(
2) You have "that guy". Someone just being a total ass in the group and ****ing everyone off. If a majority of the group wants him gone we should be able to boot even in a quest.
3) Raids. Why is it in pug raids there seems to be that one person who won't listen and does his own thing often times causing lots of unneeded issues. Let us boot them plz. I am sick of people in FoT running to the reaver and then spreading the "boom" to everyone else. Listen to directions or let us kick them.
Now I know the biggest drawback to this would be abuse by those who are just jerks or elitists...I don't care if people boot me for stupid reasons I know not to join them anymore and its not a big deal. Being able to get rid of the trouble maker would be a very good option.