OK, this isn't the most scientific thing, but 'who do you trust' brings up 400K results on Google, while 'whom do you trust' brings up 150K, and the first result is an article on exactly this topic(1).
So obviously what's "proper" or not depends on what dialect you're trying to conform to. I can believe that if you're part of that narrow, elite sliver that would naturally use 'whom do you trust', the "incorrect" use of "who" as the object of a sentence must seem garish, but to the rest of us, trust me, "whom do you trust" sounds ridiculous.
