Interesting Point

One of my readers brought up an interesting point for debate on the "whom" topid. Personally, I think the debate on "whom" has kind of exhausted its interestingness, but here's the topic anyway: "Resolved: 'Whom' is not a necessary word". I agree with this, but does anyone know of any case where using "who" instead "whom" results in any ambiguity? Most of the cases I can think of are not ambiguous at all because of word order.