Remember the day when we all thought that the site is down for about an hour? At that time, some of us (yourself included) were kinda forced to create new accounts. For example, if you go to users page and sort by name then you can find you (TRAD) and another you (TRAD 1) on page 124. Since both accounts point to the same email address, you get 2 emails instead of one. I believe that the merge with Oracle questions caused some of these second accounts to become re-enabled. It will probably take to contact Chris Massey to get this issue resolved.
P.S. I did a spotcheck on few names and it appears that other accounts which were created on that day (Fatherjack 1, Kev Riley 1, Oleg 1) are not listed. This explains why I don't get double emails.