Can speaker cables damage amplifiers?

Well, I don't know what it means in this case (common usage), but I can tell you what it means in layman-engineering terms. Take Rockvirgo's email, the part about the wave being reflected back negatively. If the power amp has a feedback loop, it'll see that reflection, and try to correct for it. The feedback loop is fast -- but not instantaneous. Depending on the signal, the reflection, and the speed of the feedback loop, the amp will just never get the output right. First it'll try to push the power in one direction, overshoot and go back the other way. If things get really bad (you get some resonance) the amp can diverge wildly from the intended signal. But, if you have a reasonably talented person designing the amp and feedback loop, this won't happen -- at least at audible frequencies. Maybe this is why rumor has it that high bandwidth amps can be more prone to this effect? It's been a long time since I've done any engineer stuff -- looking back is a bit fuzzy.... Perhaps someone else can improve on this explanation.

It's my understanding that if a speaker cable's own charactersitic impedance is too low, that this is what allows the wave to reflect back into the feedback loop of the amplifier.

Oscillation? Have you ever seen the footage of that large suspension bridge that started rocking with the wind until it self-destructed? That is oscillation.

Good one.

There's so much here, I hardly know where to start. First, in my opinion, if an amplifier can oscillate just because of using a certain brand of speaker cable, either the amp, or the cables, or both, are poorly designed. Second, oscillation is a signal coming out with no signal going in. Oscillation occurs in an amp when specific conditions are met regarding the resistance, capacitance, and inductance values connected to the amps input or output. The analogy to the bridge is a good one, or think of holding a mike next to a speaker in a PA system- you get a howl or a whistle. An amp that oscillates because of the speaker connections will put out a signal even if the inputs are disconnected; this is usually called singing (it's like a dog whistle at high volumes.) The amp will have a bright, edgy sound, because of all the distortion caused by the oscillation signals, and the output transistors will get very hot. In a really bad case (think dog whistle at 100 watts), all this happens in a few seconds, and then you get silence, because the guts of the transistors are now little melted balls of metal. (The next sound is usually the owner crying.) This situation just shouldn't be able to happen with changing cables. Last, I have a lot of respect for Pass, and what he says is true, but irrelevant. The cables are too short, and frequencies are too low, for there to be a significant reflection. Reflections are a problem when the cables's amplifier end is at one voltage, while the speaker end is at another (the amp is already putting out note B while note A is just getting to the speaker.) Don't worry about it until your speaker cables are over a half mile long. My apologies for the long post.