An infocalypse would be a time when our
info or our
ideas and knowlage would be done away with, by a crash in it's system.
Much like the fall of
Babel.
In
Snow crash it is presented in a time when the world is one whole, with roads and
burbs and various countries within even
America, when the world speaks a primary language (
english) and the
internet is in an amazing form. But all of this can be fouled by someone who wants to take the world over, by placeing his ideas within the system and killing the
hackers, or the keepers of the info. He kills the hackers with a
nam-shub, which is a virus, which infects the hackers. It also takes over
normal people and makes them easy to influence and use because there is a mother language that is inherent in every person in the world, and snow crash uses that to take over their minds. At least thats the idea it presents.
To sum up the point, an infocalypse is a thing that would destroy a world too wound-up on info and being on the "fast-track", if it is indeed something real.