A thing is AntiFragile if it gains from disorder. If it becomes stronger as smaller parts inside it fail or change randomly.

The WorldWideWeb is AntiFragile, there is no central control, any of the servers in the WorldWideWeb can be up or down at any time, they are individually fragile, but the probability of many of them being down at the same time is very low, so the chaos of the lack of coordination between the companies using the servers, actually makes the WorldWideWeb gain from disorder.

The WikiWikiWeb is AntiFragile, there is no central control, anyone can change any page, to improve it or to vandalize it, they are individually fragile, but the probability of many of them being vandalized at the same time is very low, so the chaos of the lack of coordination between the visitors, actually makes the WikiWikiWeb gain from disorder, there is always more people trying to improve the content and revert vandalism than people trying to cause damage.

Metals tend to become harder and stronger (but more brittle) as their crystal lattices become more disordered.  This is because energy is required to propagate a bend or crack past a crystal defect.  There is a limit to this effect -- a sufficiently disordered "crystal" is a liquid, not a crystal.  Tempering and annealing are processes used to change the number and size of crystal defects in a metal.

Anonymous is AntiFragile. If one of them is taken out, it only makes the rest try harder. And because they are anonymous, and have no head count, their numbers are unknown, and more may become anonymous at will.

''Perhaps an example or two is called for here?''
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See: FailureIsInevitable