Reading your comments, rlbl, I remember them changing it up somewhere in MW2. I want to think that it was because of the Javelin ... people team killing on the first spawn. But in CO4 and WaW, what I described earlier was very close to what they had. It did not prevent troll killing, true, but it did limit what they could do. Usually trolls would get frustrated at having to sit out for a full minute and just back out of the lobby. Isn't that what we want?
Hey, I'm guilty of accidentally killing teammates just as well as anyone else. I've even been kicked from games for too much TKing. But, overall, it is not difficult to avoid killing teammates. In all of COD history, the only two maps where I thought it was "easy" to TK were Shipment on COD4 and Rust on MW2. But those were two of the smallest maps in COD history, too (if not THE smallest maps ever). IMO, on those maps, TKing was a given. On Shipment, as hard as it was to not TK, there was a huge effort to avoid it - otherwise you had to sit out for up to a full minute.
As far as the streak rewards killing teammates, I do have to disagree with you there. Without that, at some point you'll end up with another Chopper Gunner or AC130 that can run up easy 100 kill streaks.