As a linguist, I can say resolutely that your prescriptivism is basically pounding your fists against the immovable brick wall of change. All types of case are rapidly disappearing from English. It's a continuing trend and has been for hundreds of years. The ambiguity generated is a trade-off people make for a variety of conveniences, let alone to fit in.

The subjunctive mood is basically gone from practiced speech, too. None of it is terribly worth lamenting.

In fact, changing it to "whom" would do nothing more than alienate its large-scale market, who aren't all leather elbow pads and Strunk & White, but rather real people who exercise language outside of the confines of a book report.

Sorry, dude. It's just not worth getting bent out of shape about.