Who knows, maybe you witness a deadly barroom brawl about to break out over whether George Clooney really did appear in the fourth season of Facts of Life. Or maybe you need to know the elemental number of yttrium.
Or, like me, you're a librarian and can't stand the idea of keeping people away from information that's free and readily-available.
Whatever the case, if you absolutely positively must use Wikipedia today, try:
http://en.m.wikipedia.org/
(The mobile version of the site, but it runs on your browser just fine.)
Another option, of course, is to use the other language versions. Makes a good excuse to practice your Spanish, French, or Esperanto.
Have fun, and keep learning.
N.B.: I am posting this diary, not because I think the blackout is a bad idea, but because I think it is working so well. As we have seen, politicians (some very surprisingly right-wing ones) are already backing away from SOPA/PIPA like it's radioactive.
So, I think, a little surreptitious 'pediacizing can't hurt.