NoReg

As you were bending the heck out of it, or during the initial crash, did it seem that the bending occured all in one small area, like where the welds attach the the seat tube, or the bridge, then you have a possible problem in a concentrated area. If you were just bending the tube, it might be as well to look at the tubes themselves, do they have fancy S curves in them? It's not as though all bending is fatal.

The other thing, is that your main loads riding the bike are in the vertical axis. The bending may have weakened the tube in a horizontal axis (and assuming from the above check you have ruled in or out damage to the joints) but for the most part that is pretty lightly loaded.

Also it is the rear end. I'm not saying nothing bad happens if it falls off, but is it likely to collapse all at once, and even if it did... The fork is a different mater, if it collapses it's potentially fatal complication. Let's say you had a aluminum fork, and you crash it so your wheel base shortens an inch or 2, then you bend it back forward, well if that goes it could be interesting. What are we talking about here? Is it a comuter or are you racing it downhill?

I'm not trying to talk you out of trashing it, that has to be your safe option, but you can also analyse the specific tweaks and try to rule various failures modes either in or out. If there aren't any dents crimps, kinks or heavy workings of the welds, it starts to sound more like a general bend, one that spread the strain over a large area. So you would be concerned about being in a place where a certain force applied to a tube across a wide area was sufficient to cause the whole tube to blow. That would be quite a trick.