I don't know...I think it's possible that Obama held back for the same reason Bush never responded to the ridiculous 9/11 truthers...because the nuts who really buy into these conspiracies aren't worth responding to. I mean, if he was going to hold back for political reasons, why not wait until next August or September when he could marginalize his opponents just before the election?
Obama probably should've continued ignoring them. Beerfan will show up here in the next couple of days and show us why releasing the birth certificate was a waste of time. He'll have rationalized it somehow and will point out "flaws" in the birth certificate that was released, concluding that it was a Photoshop forgery.