Wikipedia's sysadmins should make sure their blackout pages return an HTTP 503 (Service Unavailable) response so that they don't accidentally poison the search engine indexes, which risks causing SERP problems well beyond the protest period.
There's a saying that goes, "If you owe the bank $100, that's your problem. If you owe the bank $100 million, that's the bank's problem." In this case, that would be pretty much Google's problem.
It's just going to be an overrideable div. You could adblock it right now if you wanted, the div ID was already announced somewhere or other.
We're aware of that, thanks! I explained that to one of our sysadmins and I think we came up with a solution, although I think it will be more like blocking the blackout JS for search engines. I'll double check this is in place tomorrow.