They replied to my support ticket as follows:
Ticket #****: Re: [Mt.Gox] Password recovery
Your request (#****) has been deemed solved.
To review, comment and reopen the request, follow the link below:
http://support.mtgox.com/tickets/****
Jiraiya, Jun-28 18:33 (JST):
Hello,
We have identified an issue with our password reset system that caused many users to receive unsolicited password reset emails. It is likely this was the cause of you receiving this email.
We would, however, like to remind you that having the same password for multiple online accounts is not secure.
Thanks,
Regards,
Jiraiya
MtGox.com Team