Can some newbie explain to me why they feel it's necessary to double or triple post? Is your freaking question so important that it has to be posted multiple times or in multiple sections? 9 times out of 10, the post doesn't even contain a proper question or enough information to even attempt an answer. Try thinking before hitting the Submit button!
Check the submission times for the multiple posts.
I think most of the double posts are due to the slow forum software/database.
A newly submitted topic will look as though it didn't 'take' and someone not familiar with slow software response will be tempted to hit the submit button a 2nd (or 3rd) time.
So if you see multiple posts with time stamps that are identical, or nearly identical, it's the slow software tempting a 2nd click.
The posting a topic in multiple sections is something else altogether.
If I hadn't 'double-clutched' a few topics myself I'd say it was just a software/database glitch.
But I know I've hit the submit button twice and had that same result.
Not going to say it can't happen with one click, the software/database is amazingly complex (and buggy).
But there are those times when you press submit and nothing seems to happen - pretty tempting to hit submit again.
If they are almost the identical time, they are getting click happy, and it's being submitted multiple times. If there is a little time inbetween (such as 5 minutes), then they don't know how to find their original post, or are being impatient.