The problem with predictious is the same as the author identified unfortunately - the currency used is bitcoin, so if you're right and the price falls, you could still lose money.
I would love if one of the major european bookies (e.g. Betfair, Bet365, William Hill, Paddypower) would let you place bets on the price at a given time in the future, in your local currency like euros. Bet365 already let you do this in major currency pairs, as do other bookies:
As I pointed out in another thread yesterday, the problem is potentially even worse than just a price fall; if Bitcoin falls sharply enough (and/or governments wade in to restrict Bitcoin use) most of these startups with a Bitcoin-based business model won't survive to pay up.
I'd have thought the specialist financial spread betting firms would in theory be best-placed to be a trustworthy shorting option for Bitcoin bears.
Yeah what you're describing is a well known phenomenon in financial markets called counterparty risk[1]. Those betting against the subprime mortgage bubble prior to 2007 for example feared that those institutions accepting their exotic CDS bets would actually go out of business when the subprime bubble popped[2], and the bets wouldn't be realised.
It's a sign of immaturity of the bitcoin economy that there's no trustworthy effective bitcoin shorting options- even if you don't wish to speculate, but because you wish to hedge your exposure to bitcoin volatility (say you're a large ecommerce player, with significant bitcoin holdings- you're effectively long bitcoin - and you don't want those holdings to halve in value overnight).
And 796.com offers a kind of bitcoin price futures that you can use to bet on falling prices - not outright shorting, but close enough.