If you have the money, more power to you. I think more then one is over kill but since apple is marketing this as a piece of jewelry, i.e., fashion, having different versions makes sense to those who have the cash to buy them.
I am going to buy at least the sport and the steel version launch day (extreme or normal outdoor / gym activites and formal occasions & work) because I am going to eventually give them as gifts to my siblings so we could use them right away (they cannot afford or may not be available right away on where they live).
A third purchase depends on the price and/or exclusivity on some functions of the gold Edition as a collection / home use only.