I've just tried to turn my email alerts off, so I unticked all boxes and clicked "Update settings". When the page refreshed, all the boxes were still ticked but my email address had changed to that of another user, towelinmonk (www.instructables.com/member/towelinmonk/ ). I'm not sure if this user is actually now receiving my email alerts, but I thought I'd best report it anyway. I've changed it back now, by the way.
As a side note, i've also had to switch to firefox from chrome to post this, chrome wouldn't let me post the topic (Win XP).