For instance, the ever-popular and agony-inducing "I wish you would have [called me earlier/not spilled Perrier on my topsiders/died in a fire]." I'm not really sure what this means, and I suspect the people who use it do not know either.
It's also awkward and unwieldy. For example, "I wish you would have not spilled Perrier on my topsiders" sounds horrible. But "I wish you had not spilled Perrier on my topsiders" is straightforward.
"I wish you had called me earlier." That makes sense. Why introduce the other conditional? It does not belong in the apodosis, fools!