Great thread, every thing's been said pretty much, but id like to point out one very obvious and therefore usually overlooked form of elitism. Pop music! Have you ever tried telling a (lets say) Beyonce fan that you dont find her latest single the best music ever made? Go and try it out...
If elitism is defined by the amount of close-mindedness and paranoia demonstrated by "aficionados" of a certain genre/artist, then pop music likely takes the first place. I spent some amount of time trying to defend those "stars" from common accusations that they "cant sing" or "have no talent", but, there came a moment when i realized that theres more than enough casual people taking their side with bias! Everything is ok with those people. You can sign a multi million contract with mass-murder corporation, or ally with some notorious politician, or have a private island and pretend to be a "philanthropist", or abuse your body to "market" your music, or even use auto-tune if you will, do anything that is ethically questionable, its still being "modern" and up do date with latest fads and trends to those people.
So, even though i developed my own brand of animosity towards classical/jazz/metal elitism, i would say that, surprisingly or not, "casual people", with their inclination to defend their "stars", and with their "with or against us" attitude represent the most widespread, aggressive and oppressive breed of elitism. Furthermore, i even feel as though afore mentioned elitisms are more than justified by reasonable desire to distance themselves from this stupid world of hypocrisy, demagogy, and popular taste that rules "mtv" realm.