It would be very easy to write a program that would, every week say,
randomly select three bits of text from every Wikipedia page and search
on that text using Google. If there were any results--well, it's hard
to say how the program could tell if there were zero results--this could
be posted somewhere for a human admin to check. That's the general
idea. Of course, it could be tweaked, but I'll bet something like this
could be made to work.
Larry