User blog comment:Jenburton/An Update on Message Wall/@comment-2048489-20111001141704/@comment-1154266-20111001221946

I read this to imply that it was optional: "When we originally made the announcement on Monday, we understood that turning Message Wall on and off was not technically feasible. We’ve since learned that it is possible to turn the feature off and on (and, with our help, the test wikis will be able to do so)."