I just got at least 12 backburner kills by camping behind a teleporter exit. Then the round ended. I think they were making fun of...something. Me. Themselves. Existential indifference.
Epic fail comms combined with a "pants-on-head-retarded" Engineer.
Camping enemy teleporters is a very valid tactic (I do it all the time myself & hate when I have a camped exit a teammate destroys) but you shouldn't be able to get more than a few kills before the Engineer respawns & destroys the exit unless they're devoid of a clue.
Stuff like that is very situational though. For example I got 57 destructions as demoman without dying once & my rampage was only stopped by my team winning the round. It was the day after the Engineer update released & I had a friend playing medic with me on cp_steel.
However this is a bit of a digression from the topic