It is not possible unless the user voluntarily associates his personal information with that mac address.
It is possible to harvest this information covertly. Up until iOS 7, it's possible for any iphone app to get your mac address. So if you also provide your personal information, an app could covertly associate them.
It doesn't have to be voluntary. If I have a list of all the MAC addresses/timestamps and can cross reference that against a different known list of people times (ex: credit card transactions, rewards card, even face recognition) then you can associate them. With enough data it can be very exact.
