I played some UT4 until I got banned in BTA for stealing HP bubbles (that drop off players after you kill them). Some guy was whining a few times cause of that - which resulted in a ban for me. After having me, doing all the work and deal 195 hp damage to the enemy player and then having my teammate killing him by dealing the last 5 hp damage.
I got banned for that.. in a game with a community of 10 players.