Honest question here about the risk of being “unique”...:

If my unique identifier changes with each browser version + os version + timezone + build id + fontpack + screen size... am I really trackable through this vector? Those things change all the time for me at least. Seems like a very short term method of tracking at best. Why should we be afraid of these things? I had the same question about panopticlick (or whatever EFF called it).