Japan's financial regulators have been reluctant to intervene in the Mt. Gox situation, saying they don't have jurisdiction over something that's not a real currency.
They pointed to the Consumer Affairs Agency, which deals with product safety, as one possible place where disgruntled users may go for help.
The agency's minister Masako Mori urged extreme caution about using or investing in bitcoins. The agency has been deluged with calls about bitcoins since earlier this year.
"We're at a loss for how to help them," said Yuko Otsuki, who works in the agency's counseling department.
It's hard to know how many people around the world own bitcoins, but the currency has attracted outsize media attention and the fascination of millions as an increasing number of large retailers such as Overstock.com begin to accept it.
Speculative investors have jumped into the bitcoin fray, too, sending the currency's value fluctuating wildly in recent months. In December, the value of a single bitcoin hit an all-time high of $1,200. One bitcoin has cost about $500 lately.
Roger Ver, a Tokyo resident who has provided seed capital for bitcoin ventures such as Blockchain.info, a registry of bitcoin transactions, said he believes bitcoin will survive, possibly emerging with better technology that's safer for users.
He said Mt. Gox people were likely sincere but had failed to run their business properly.
"Mt. Gox is a horrible tragedy. A lot of people lost a lot of money there, myself included," he said ahead of the bankruptcy filing. "I hope we can use this as a learning experience."
Some countries have reacted sternly to bitcoin's emergence, but many people remain fans of its potential.
Vietnam's communist government said Thursday that trading in bitcoin and other electronic currencies is illegal, and warned its citizens not to use or invest in them.
