I am also very interested in the question of personal identity. However I tend to phrase it as a question of "self" rather than identity. Within sociology and social psychology "identity" usually refers to a specific role a person dons in a particular setting. While Identity is the totality of roles they contain in their cognitive wardrobe, the process by which they create/delete identities, and the apparatus for choosing to take on an identity.

I also have much to say about hats, but I would to hear what you think of the above stated ideas before I continue.