Our phone call to Sony tech support left us with ambivalent answers. Our representative explained that if a third-party cable caused our PS3 to short-circuit then, quite obviously, Sony would see that as the fault of said third-party and not their problem. However, if the problem was seemingly unrelated, such as a failure of the Blu-ray drive, the operator's response became less clear.
The Consumerist dug into the PlayStation 3's warranty and found a clause that rather unclearly states that you assume the liability and risk of using non-Sony products with the console.
We contacted Sony and received the following official statement:
At SCEA, we have the same warranty for PS3 as we have for the other PlayStation platforms. Our Customer Service department will trouble shoot fully to see what the set-up environment is and what may be causing the issues. We are determining more info about this specific instance. In typical situations, video cables would not void the warranty, but each situation is unique.
In other words, buyer beware. Through Froogle we found some first-party PS2 component cables, which are compatible with the PS3, for sub-$20. For that price, you're better off being safe than sorry.
[Via Netjak; thanks to the very many people who sent this in!]