Just because lazy people in North America couldn't be bothered working it out any more doesn't mean Twitter shouldn't set a good example. Ignoring it is not correct, the distinction is correct. It's not a dialect, either, given that it's, uh, the original.
Given that there already is an official distinction between "American English" and "British English", I don't think your comment is very correct. It might be just another rule to add (actually remove) in the A.E. schoolbooks.
Languages evolve. If enough people drop "whom" in America, arguing about this change would be like arguing about whether sweets or candy is "correct".
This still doesn't make it a dialect though :) Sorry, but it just annoys me to see American English fanatics say how British English is "wrong", or a "dialect" of American English when it was the original base of American English to start with :)
I do agree with you, languages evolve. But that doesn't mean we should just drop grammar altogether. I was a little snappy in my original response, and I apologise for that, but the sentiment is still the same.
Saying American English evolved from British English is just as false as the reverse, and just as false as saying humans evolved from monkeys. Both evolved from a common ancestor. British English has changed just as much as American English has since they began to split in the 17-18th centuries.
