Over the past 15 years of working with home computers, I could not help but notice the insidious spread of the ubiquitous mouse. First the lowly rodent appeared with the Macs, had only one button and could mate only with the Mac keyboard. With time mutants appeared with two buttons, and Logitech even shipped adapters with their mice so that if their mating organ was the wrong size or shape, an adapter could be used to allow mating between an even greater number of species. As with any biological species, as you widen the gene pool, you produce greater diversification, some would say more mutations. One can only imagine with horror the results that would be manifest if similar mating adapters were available for other species.
Mice introduce a whole new set of problems for the computer user.
Usually dirty balls is not the problem, its just that the little wheels get coated with a mixture of dust and oil. The balls may be in perfectly good condition, but they can't move the wheels. It just goes to show that good balls cannot always move the wheels of industry and commerce. I work on a network shared by several hundred adolescents. One problem we have on our network is that of missing mice balls.