Tube failure -- what would happen in worst case?

I guess I was lazy and ignorant. I assumed that a new tube amp was factory biased and I should not fiddle with it, and also I did not want to damage my amp by screwing up. Now I feel like I need to know more about biasing.

I guess, this shows what would happen?
http://www.youtube.com/watch?v=_KOjn9ii2Jg&feature=related

Thanks for all.
I did not bother to bias my tube amp, and I am selling one (Chinese made) and get an amp with auto bias feature (BAT vk60).
Any way, is this a good reference for biasing?
http://www.aikenamps.com/Biasing.html
Any of you have other source?

I had twice tube failures on my Chinese MC10L.
Both times, a fuse and a register sitting next to the tube blew off, and smoke came.
First time it happened a couple of months after I changed the whole four tubes. After that, I learned how to set the bias.

Second time, it happened in an apartment that I moved to. It was a new place and I did not change the bias. It happened a month after the move.

I also had a tube failure for my BAT vk60. It happened when I tried a seemingly bad power tube. A second after powered up, the tube got bright and failed. Also, a fuse and a register blew up. I replaced the register, fuse, and used a new set of power tubes, and then it worked work OK.
I still have both amps.

After these three instances, I became more careful about using tubes and setting bias. And, I feel that it is NOT a big deal if tubes fail. Looks like the registers and fuses do their job to protect other parts of the amp.

For those who want to try tube power/integrated amps, I would suggest to try with cheap amps first before moving to more expensive models.