I did this to my friend once, because he placed his tac in the truck trailer on Arkaden.  But I let him go after a couple of seconds.

I have never been blocked though, except for one time a teammate threw a decoy package in front of a spawn point on mission and couldnt get out.

Are these party member doing it, trapping you from both sides?  I would report them for cheating.  I guess that would be the best one to describe that under, or exploiting.

     I bet the OP is referring to Infected, which makes it hilarious. Since im never the guy being trapped, i usually find it pretty funny when i randomly come across someone who is trapped in a corner by some dude.

     And no, nothing can be done.

That's been going on for a long time bud. All iI can say is to stay out of the corners.

Stop camping...

Happened to me last night once, went to go put my headset on and in the matter of ten seconds I was trapped. That's the ONLY reason I miss TK'ing. Only thing they do is laugh it off. Oh well another day, another piece of BS. =p

I do it to a team mate camping in domination and not playing the objective. It's especially fun to anger Bush Wookies.

Honestly, just refrain from corners. I absolutely hate playing an objective game and my team camps in a corner the whole match. I hate camping in general and the closest thing I've done is call in my reaper and hide in a bush.

Simple answer, if your calling in a killstreak, never go to a corner just go into a bush or behind a wall, etc.

If your reloading, hide somewhere else for a split second.

Otherwise, man up and just play smart without sitting in corners.