During half an hour's rooting around through Hackworth's skin, roaming 
around an area perhaps a millimeter on a side, they observed a few dozen 
artificial mites, not an unusual number nowadays. Almost all of them were 
busted. Mites didn't last very long because they were small but complicated, 
which left little space for redundant systems. As soon as one got hit with a 
cosmic ray, it died. They also had little space for energy storage, so many of 
them simply ran out of juice after a while. Their manufacturers compensated for 
this by making a lot of them.