If I can put forth my 2 cents:
The "who/whom" distinction is so unclear to even most native speakers simply because "whom" is almost completely dead on this side of the Atlantic (I'm in the US and don't know much about British usage). It has been completely overtaken by "who" in all contexts, across the board.
What it's really used for these days is to separate people into classes based on level of education (and even that has largely waned as well, due to the aging of the population that was educated in that fashion). In other words, it's not an issue of grammatical correctness; rather it's a social status symbol to be lorded over others.
In other words, for all you non-native speakers out there, learn the "rule" if it's required on standardized tests. Do NOT include it in your own writing as you will sound stilted. And finally, avoid it in speech at all cost!