I love this response from Coke the Diet-Coke Mentos meme which raises a few interesting talking points:
1) A late response is better than no response at all
2) Large corporations absolutely can "fight back" (and I say this completely light-heartedly) and join the conversation...as long as they talk with (as opposed to at or down to) the comunity
Not sure how the challenge will work out, but moreover it makes for great storytelling and humanizes the brand in new and bold ways.
PS An anal reminder that The Coca-Cola Company is a client (of which I am very proud)