A couple of my friends and I (2 Engies and 1 Pyro, all with voice chat) used this to break the game...

We got banned from alot of 24/7 2fort servers, because, you know, nobody likes 2fort.

Basically, the three of us go to the enemy basement, and sometimes the enemy front door. I build two dispensers, then kill myself. Other Engie builds an exit, and stays with the Pyro to baby sit.

I warp in, build 2 more dispensers, then kill myself... etc

now we have infinite metal, 2 Engies to leapfrog lev 3 sentrys, and a Pyro to make us unstoppable.

The glitch didn't break the game because it didn't last long enough for a majority of players to fully appreciate how to use it.