I get identical emails with identical time stamps for the same messages. They happen quite frequently with SB (hundreds of emails since the upgrade), and I've never gotten another email duplicated.
They're the exact same emails. I could leave the house for a day, and when I came back I'd have plenty of notifications... every second or third SB email would be duplicated.
At 4:56 today I got three copies of a notification for the "The Other end of the DIR debate" thread, all together with the same time on them.
It's nothing on my end.. it happens whether I use webmail or Outlook Express, and whether I use an email account hosted by GoDaddy or Time Warner.
I'm obviously not the only one this is happening to. Like I said, it's *only* scubaboard emails.