Two Amps One Pair Of Speakers

I've read posts here on audiogon stating not to connect two amplifiers to one pair of speakers because (as it was put) the stronger amp will win if they are both on at the same time. To me, this means that one amp will likely have a fuse blown - however, I wonder if this is even true at all and I am curious to know if anyone out there has connected two amps to one set of speakers.

Now - I am not talking about bi-amping from a single source. I am talking about two separate systems connected to a single pair of speakers.

Of course having amps sending signal at the same time wouldn't make for good listening but even if they were, wouldn't the speakers just play both sources? Power flows from + ...> - so the positive output of both amps would flow through the speakers into the - of both amps wouldn't it??

Perhaps its just me but that seems more likely than something blowing up... but then again, what do I know?

Even in cases where someone bi-amps in a single system, there are two amps driving the speaker which in many/most cases is connected internally via crossover - regardless of how many binding posts are on the speaker. This is tried and true - lots of people bi-amp but why would it not cause damage but connecting two amps from different sources cause a problem?

Sorry for the rant, I hope someone can shed some technical knowledge on this.