shoot, a missed opportunity

Mizuho share blunder Mizuho Securities wrongly issued an order to sell 610,000 shares in J-Com for 1 yen each, although it intended to sell each share in the company for 610,000 yen. (FYI...that's about a 5,700 dollar-valued share for less than a penny!!!)
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Apparently a lot of day-traders jumped in on the fun. Oh, maybe next time. Though I have a feeling this was a 'once in a lifetime' incident...poooooO.
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12/20 update: An unemployed 24-year old man cashed in on this and made 560 million yen, roughly equivalent to 5 million USD...wowow. Ethically speaking, should he forfeit this money or is he entitled to keep it? What are your thoughts?