Who(m) created this rule?

I learned the "rule" for when to use whom and when to use who when I was in elementary school. The correct word usually comes naturally now, but if I'm unsure, I can quiz myself with a quick question as I encouraged all of us to do in class on Monday:

Is who/whom referring to she, he, we or they? If so, use who.
Is who/whom referring to her, him, us, or them? If so, use whom.

As much as I hate simplifying these terms to masculine terms, its even easier just to remember to match up the "m's" on the end of him and whom or them and whom. For example:

To whom does the car belong? It belongs to him.
To whom do you wish to speak? I wish to speak to them.
Who is your best friend? He is my best friend. (no m's in this one!)

Even though I am comfortable with the who verses whom rule, I know this is a point of frustration for many. I googled "whom verses who" and thousands of responses popped up (obviously - its google) but I found different explanations on ehow.com and ask.com. Its funny to me that people look for quick answers to grammar questions on Wikipedia rather than searching in a legitimate online grammar source.

Even though this rule works like second nature for me, I know that these tricks may not work as easily for some people. I've been thinking about the grammar rules we create to remember the right way to do things, and how some work really well for some people and are ineffective for others. I know that I am an auditory learner. If I can make something rhyme or make sense orally, I'm good. For example, I've never forgotten that FAN BOYS stands for For And Nor But Or Yet So or that i comes before e except after c or when it sounds like "A" as in neighbor or weigh. Still, these rules have their limitations.

I think one reason the whom/who rule is most frustrating because it is almost outdated. Whom has been nearly eliminated from our oral conversations and vocabulary in general. In a way, I think this is a good thing because the English language is far more complicated than it needs to be, and if we can simplify the rules that seem arbitrary or confusing, we might as well. Until its completely gone, though, I say use the she/he/we/they verses her/him/us/them rule.