What prompted this post is the fact that last night when playing 1-on-1 Mixer, I had placed my TL in the area behind the "safety fence" by the rocket launcher. I needed to reload my weapon, but silly me failed to view thru the Translocator before I used it. My mistake, as I ghosted as soon as I used it. This may be have been mostly likely that my TL had been damaged somehow, or maybe that someone was standing on it. Again, as I did not look first, a ghost resulted. Thankfully it was JUST a ghost and not an out-and-out death. Again, my bad. I think it might have been damaged (most likely though an enemy nuke), as had someone been standing on it, THEY would have been the one killed, not myself. This is point one: PLEASE try to avoid standing on someone's translocator, as it could possibly result in your death (could one of the developers please confirm/deny this for me?).
Other anomalies can cause Telefragging/Teamkilling as well. For example:
If you jump in a hole in gael (or another map where a fall down the wrong part - such as a pit, or lava or acid pool - can result in a death) and the last person to shoot and hit you it will say it killed you - regardless of it that person might have been shooting you to heal you or to TeamVamp themselves. That isn't their fault or anyone else's. Simply put, dont fall in.

If you ghost and die the lighting rod (being used by the person ghosting) could also possibly kill you, for which you will also get the "You were killed by (teammate)". Unfortunately this is just how the Lightning Rod "works". It's happened a number of times to a number of people. Most of us are aware of this, though some may not be. Now you are, so please keep that in mind.

Someone can also ghost into you, and, in doing so, essentially telefrag you. Where the ghost skill throws you is based upon mathematic formulas in the program logic of that skill. It's unfortunate when it happens, but please be aware that it does, and it is by no means the fault of the "ghosting" player. When you ghost, you are at the mercy of the game code. Please be aware of this.
Also you can be telefragged/teamkilled if you are on a spawn point when the next wave begins. Unfortunately to the best of my knowledge there is no indication of exactly where the spawn points are, shy of just being familiar with the map and knowing where they are. I believe perhaps the best way to avoid this is to keep moving, especially near/at the end of a wave. Doing so also makes it harder for the mobs to "draw a bead on"/target you. So usually motion is your best defensive option if you're not sitting in a "safe spot" where you KNOW there are no spawn points (such as the high ledge above the shock in Goliath).
Finally if you and another player go through a teleporter at nearly the same time, one may die. This goes back to the "keep moving" strategy. The WORST thing you can do is step through a transporter and just stand there in the place where you ended up when get through - this leaves you vulnerable to being telefragged when the next person steps through.
Anyhow, it is my hope that this information will help people refrain from being teamkilled/telefragged. Remember - the longer we all stay alive, the more mobs we have a chance of killing, and the better chance we have to win the map. ESPECIALLY if the lower-level players manage to survive in the later waves, as this will alter the difficulty of the mobs in accordance with the average player level of surviving players. On that note, if you see someone past wave 15 who is less than level 50 - or heck, even less than level 100 for that matter - who is hiding in a safe spot and not shooting much of anything, don't berate them - they're actually doing their part to help us win just by staying alive themselves. If you're a higher-level player, then the best thing you can do to help them and the team is to jump into the fray nearest to them and keep them covered/alive.
Thanks for reading, everyone - I hope this helps!
TEAMWORK IS THE KEY!