BitFloor's reserve of BitCoins -- about 24,000 -- was wiped out. A BitCoin was worth about $10.46 as of Wednesday, according to , another BitCoin exchange.

U.S. dollar accounts with BitFloor were not affected as well as records for accounts and trades, Shtylman wrote. BitFloor turned over around 64,000 BitCoins a month, worth some $717,000. It took a 0.3 percent commission from trades, amounting to around $2,100 in revenue for the site, Shtylman wrote.

"As a last resort, I will be forced to fully shut BitFloor down and initiate account repayment using current available funds," Shtylman wrote. "I still have all of the logs for accounts, trades, transfers. I know exactly how much each user currently has in their account for both USD and BTC [BitCoin]. No records were lost in this attack."

One user asked if BitFloor could secure some investor funds in order to pay back customers. "This would be a possibility if investors interested in helping continue operations show interest," Shtylman wrote. "It is certainly something I am thinking about."