E-mail is now reproducing in the wild?

[VirginSnow at vfemail.net]

Hi, all.  I've been receiving a lot of duplicate e-mail messages over
the past few weeks.  (Not on this list, that I've noticed, but
elsewhere.)  Has anyone else experienced this?  Anyone have an
explanation for it?

The duplicate messages that I've analyzed all appear to originate in
webmail interfaces.  Some duplicates (those from Yahoo, it seems) have
identical Message-ID headers, but other duplicate messages have
different Message-IDs.  The Received headers show the duplicate
messages getting passed along 1-5 seconds after its previous copy.  In
one case, I even got the same message three times, each with a
different Message-IDs.

Is there some new bug out there in the mail network?  Are people just
clicking repeatedly on the "Send" button in their webmail accounts?
This is not a terrible problem in dire need of fixing, but I'm curious
what could be causing it.