Here's what I think :

4 cases :

1) Either someone knows your mail address and sent a password change request

• Guy was already knowing your mail
• If you are sufficiently briefed about your security, this guy can't open your mailbox

2) Someone is spamming the website with random mails, trying to learn real ones

• More spammers knows your mail (that's not so big deal)
• It's a security breach on the website, but they can view if there is a zillion of password request
• I'm pretty sure nobody would spend that much power on the PS site, not enough people for them

3) This is a fishing mail (don't redirect on the right page)

• Definitely dangerous (for your PS account, no more)
• But you can make sure if it's a real or fake mail

4) Some guy made a typo writing his own mail and wrote yourself

• No big deal at all

Cases 2 and 3 are the most dangerous and the less probable.