Tube failure -- what would happen in worst case?

I have had tubes short out in my Audio Research M-300s. One time a tube shorted so bad it blew pieces of a resistor all over the room and took out a 1 inch section of trace on the circuit board.

Some tubes hold up better than others. The input tube in the Quicksilver full function preamp is a 12AU7 and my Quicksilver preamp ate Golden Dragen 12AU7s for lunch. One day the system was on without music playing. From the other end of the house I heard an awful sound coming from the Martin Logan CLS. The Golden Dragon 12AU7 failed. I installed another Golden Dragon 12AU7 and it lasted 2 days before it failed. I switched to a Siemens tube and never had another problem.

When it comes to tubes never say never because you never know.

I don't want to scare anyone,but fire is always possible.A simple coupling cap shorting out can cause a tube to have thermal runaway.If a tube starts glowing orange,shut if down(the gear) as fast as possible.Solid state amps,tv's, and other electronics all have risks too.Homes burn down for various reasons,a lot are electrical,or electronic failures.

As has been said, a fire is the worst thing that can happen.

Apart from that, I've seen amps take a transformer (power or output) out. That's a repair you don't want to get into.

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 did not bother to bias my tube amp

Why not?Just curious.