The interface between bitcoin and fiat always worried me. Piss poor behaviour by Dwolla if true. Dwolla and Tradehill were on the same team if you ask me: pity they couldn't see it.
If TradeHill's reporting is to be believed, I find it highly implausible it was all one transaction that was reversed. Also, there's nothing to indicate that Dwolla was the one that reversed it. They were reversed. That much is probable (although TradeHill gives different figures in every report about it). We haven't heard what Dwolla has to say about this yet or seen any evidence about it. “It's definitely true” that we don't know the details, yet.
