I've seen a vote kick initiated for players who:
1.) Were AFK or barely moving from the same spot for a long time.
2.) Players who run off in the wrong direction by themselves, instead of moving with the group, and continually get killed. When the group says "Everyone move this way" and one player continues to not do that, they are sometimes removed.

I have initiated a vote kick a couple of times in Frontlines in these situations.
1.) A player was cursing a lot at the entire team. Sorry, but in our data center people just don't that kind of thing. We are pretty calm in PvP and even if we lose, no one blames each other. But there have been a couple people who begin to completely lose it when someone dies.
Needless to say, these vote kicks have never failed.

2.) A player who spams sound macros.
"East <se.3>"
"East <se.3>"
"East <se.3>"
"East <se.3>"

Like this.

Once is enough.