Teamkilling in Battlefield 2142 doesn't make any sense. First of all, even if you are forgiven for the teamkill (meaning the other person identifies it as a mistake or even their own fault) you lose 2 points. Then if you are punished that number moves to 6 points, but perhaps that is understandable. If you got punished, you are probably being a jerk, and you deserve it.
The reason this system infuriates me however, is because of the new Titan mode. In Titan mode your team is (eventually) tasked with blowing up 4 reactor consoles and finally the reactor aboard the enemy titan. The best way to do this is for the recon class to put explosives on the console and then remote detonate them. The problem is your teammates have a tendency to stand next to the consoles and try to blow them up with their pistols/rifles/machine guns. This leaves the recon with the unenviable choice of blowing it up and taking a massive point penalty, or waiting for his teammates to move so he can detonate the explosives (which often takes a VERY long time). Even if all the people realize their mistake and forgive you, you are likely to lose 2-10 points at each console, and the problem escalates as your team surrounds the reactor.
To the devs: lower the point penalties on teamkills that are forgiven. They really shouldn't have any effect and it doesn't make any sense to me why they do.
To other players: If you see a teammate sticking things to a console or reactor, get the F$#K out of the way!
On a last note, it has recently come to my attention that teams have started defending their titan hallways by positioning themselves near an ammo crate and just tossing frag grenades down the hallway continuously. I'm not sure what the counter to this is (if someone knows please tell me), but this tactic is exceedingly lame and it makes titan assualts boring and aggravating. I don't know what needs to be done (by the players or the devs), but this tactic has shifted the titan assaults from being exciting hallway shootouts to a significantly less enjoyable charges into almost certain death. Something needs to be done to shift the gameplay back where it was intended.