I agree with MasterX.

Just for the record, The Marquis de Sade used to switch.

Identity is a strange beast. I don't consider myself, and would never call myself "a switch" or a Dom, or a 'subbie'. I do switch, but I do not feel the need for this to be an important part of my identity. So many people who get exposed to so called BDSM culture seem to become walking clichés. For example there are many people who run around calling themselves 'Doms' but are actually just 'pains in the arse's'. People automatically learn by mimicking, but the copying process is often bad, like a photocopy of a photocopy of a photocopy. I could go on about Mirror Neurons and Memes at this point, but I'd probably bore everyone to tears.

RE: human nature and categorizing. Many people see things as black and white, or shall I say they view things in a binary way. The real functioning world is rarely so well defined. There are always exceptions, or grey areas.