I didn't downvote but the closest I know you could do to this is buy an inverse ETF that is heavy in Facebook. I don't think there are any inverse ETFs that would even have more than 10% Facebook.
True, but you can short the stock from elsewhere in your portfolio (i.e., just a standard nonretirement account), and it's economically equivalent (modulo some stuff with taxes).
EDIT: for those downvoting, please point to a retirement vehicle that does support shorting