"A. Because it breaks the logical order of conversation.
Q. Why is top posting bad?"
The quote above is from David Walters, on the UK IT industry mailing list uknot, and it's a very good example of the standard arguments against top-posting: it's witty, accurate, condescending, and does nothing to solve the problem.
In the same way that HTML email isn't intrinsically evil, I can't honestly see great moral differences between typing your reply before the original email (top-posting), and typing it after the quoted email (bottom-posting). In the good old days before the September that never ended, everyone bottom-posted; now there are two ways of doing things, thanks to Microsoft Outlook (and similar programs) letting loads more people send email. The question is, how do we reconcile them?
Often I'll get hideous monstrosities of top-posted emails like the following (ironically snipped to avoid you having to scroll for ages):
Sam, can you do something about this?
-------
From: client <email address>
Subject: Re: whatever the subject was
(some more headers)
Yes, but I still have this problem.
Look, are you going to fix it or not?
On 23rd July 2002 you wrote:
> On 21st July 2003 you wrote:
> > I've got this problem
> > It goes something like this
> You're foolish. We tell you not to do this. It's your fault
>
> --
> stupidly long corporate signature that
> goes on for ages
> (as in, much longer than these three lines)
--
stupidly long corporate signature that
goes on for ages
(as in, much longer than these three lines)
This email is, clearly, a mess. That huge signature is repeated twice for no reason, it becomes difficult to work out who said what, if you read from top to bottom you see messages that, chronologically, occured in a different order (4, 3, 1, 2) - yuck. There's no easy visual way to determine, from quoting levels, how many removes from the original poster any given section is. Often, when I get these sorts of emails, I end up reformatting in top-posting order, getting rid of cruft, just so I can understand what's going on.
Bottom-posting proponents encourage people to do this at every level, so any time you get an email, all the salient points of the previous email are in the proper order, and the cruft has been stripped out. The idea is that you're being polite to your correspondent, and I like this attitude; I try to do this myself, but there are two problems. a) it takes time and effort; and b) beyond the obvious, "cruft" is subjective. Top-posting (and, typically, the corresponding lack of editing) often mean that you get the entire email exchange history, which can be invaluable for someone entering the conversation at mid-point. Once you've waded through the 10-line corporate signatures...
We need to understand that the old guard use email differently from more recent arrivals on the Internet, and rather than bitching about newbies being stupid, we need to work out how to educate and understand. Bottom-posting is useful for in-depth, point-by-point rebuttals involving many people; top-posting is appropriate for casual chat where people don't need to refer to previous posts because they remember them. My mother top-posts, and I can't honestly say that she's wrong.
While we await the result of this Internet version of the Great Vowel Shift, there are some things we can do to minimise annoyance.
First off: those two huge signature blocks. It should be trivial to strip those completely, or, if in a particularly anal corporate environment, only include that hulking montrosity of legalese once. This isn't hard.
Secondly: the main problem with the above mail is that top- and bottom-posting are used in the same conversation, and two quoting methods are using: different levels of indentation with chevrons (>), and explicit forwarding without quoting. It shouldn't be hard to build tools in an email client that can harmonise messages to either top- or bottom-posting, in which case the problem goes away.
I'm sure there are others - in a world where we have Google, it shouldn't be difficult to automatically correct attributions ("You wrote" beomes "Joe Bloggs wrote") if the email client realises this conversation is being opened up to a third party. So, readers, bug the people who write your email client and demand that they add easy-to-write features that make your life better.
