I don't know why they gave away the \a clue; you'd think they'd want to select for people who want the job bad enough to actually have a Reddit checkout.
All in all not that much of a stumbling block for anybody determined enough, but I think it will drastically cut down on the number of unusable applicants as long as the answer isn't leaked.
Alternatively they could leak a false answer themselves and disqualify anybody that sent mail to the false answer.
Everything was an easy lookup though - and a quick Googling of the answer turns up a few anonymous nobs who've already put it up on various Pastebin-type places already!
And one not-so-anonymous non-nob HNer who seems to have deleted a tweet, but The Google Never Forgets (tm) :) You know who you are!
[Edit: on second thoughts, removing link to screenshot, even though it was heavily edited to avoid spoilers.]
Curiously, no results show up on Bing though - even for the answer string.