How many bikes should I own?

Owning multiple bikes is not necessarily consumerism. The riding that I do can be quite different, just like I have several pairs of shoes for different walking (although at one time I wore only one pair of sandals).

I would like 4 bikes:
1-Low end racing bike for riding with my club. I would trade the stock wheels for the lightest but strong wheels around. That is where weight matters. Carbon? Maybe, I hear it really is good for the vibrations but I think it makes it too pricey for me.
2-a mtn bike that is unbreakable, always set up with racks and ready to go for 3 day bush bashing trip. Thorn proof tyres, etc. Maybe a rear shock if I can figure out a rack that will carry 20lbs back there. (picture should be hear)
3- a commuting bike, one that looks like shit (no one wants to steal) but rideable. Probably 3 speed, dynamo hub for lights, fenders so I don't arrive all muddy, bell, No bottle cages, and the like.
4- touring bike that can take rough roads, ready to ride to South Africa.