As a veteran of Usenet, I’ve only grudgingly come to accept the practice of putting all responses to an email in a lump at the top, with the quoted text below. I much prefer to have the responses interleaved with the original points being responded to. I’ve pretty clearly lost this one, though, and I’ve learned to live with it.
One consequence of this practice that continues to drive me nuts, though, is the way that people have become conditioned to believe that nothing below the first quote header exists. This is exacerbated by things like GMail, which explicitly hides quoted text. Thus, I’m constantly getting emails which consist of a couple of sentences of new material at the top, followed by ten levels of quote-and-reply going back a week or more. This is particularly entertaining when the whole thing has been forwarded to a mailing list or group alias, and the quoted material includes a lengthy discussion of who should forward it in order for the message to have the greatest impact, giving a cynical air to the whole thing.
Look, people: the delete key is your friend. There is no need to send every bit of the exchange on to new people. If you’re only responding to the most recent email, do us all a favor and delete the rest of the quoted text. If you’re forwarding something on to a new audience, delete everything but the most essential part of the message. We don’t need to see all the deliberation that went into the decision to forward: just send the key message.