It was speculated somewhere that Wikipedia might block Google from searching as part of promoting the Wikipedia search.
Aside from the suspicion that the Wikia search function will be a clunky heap of junk and will be unable to compete with the mighty Google, and not being accessible from Google would be a slow and painful suicide, would Wikipedia have the right under GFDL to stop Google using the articles?
(At least Google doesn't trash articles while it is scanning them, unlike those noble fellows at Veropedia).
Presumably, if they were so minded, Google could just create a bunch of temporary unsigned Knols out of Wikipedia anyway, ready for someone to approve or reject as appropriate.