It's encouraged by Microsoft e-mail packages putting the cursor at the top of a new reply, with the "Original e-mail" underneath.
If you blindly put the cursor at the bottom, you get bottom-posting, which is almost as bad. Some user education is required to teach them to cut all the irrelevant stuff and to interleave responses point-by-point.
Xnews (a nice Win32 newsreader) has the nice feature that it bitches at you if too much of your post is quoted text. It also has a toolbar button that skips to the next unquoted paragraph, making it easy to navigate interleaved responses. (Are there any good Linux-based newsreaders comparable to Xnews?)
