More than 800 crypto currencies are currently live...
Bitcoin is on the rise again - it's helped the total value of cyber currencies to increase to more than $50bn.
Since the first Bitcoin spike in late 2013 investors have been paying attention to the online currency, which has been treated more like a commodity by many.
Its value has increased by 286% in the past 12 months and hit a new record value against the dollar of more than $1,800 late last week.
Ajit Tripathi, a director in fintech with PwC has warned that it is dangerous to have this level of money tied up in this (often volatile) market - he is particularly worried about the number of new online currencies making initial coin offerings (ICOs).
"An ICO issues crypto tokens rather than stocks and bonds, but that’s irrelevant to the substance of the activity, which is raising capital from the general public," he told The Financial Times.
He has warned that the market is operating outside of standard financial rules: "Capital raising activities need to be regulated to protect investors ... The question is how sophisticated are these investors?"
Away from Bitcoin, more than 800 other online currencies have been launched in recent years.
More than $1.5bn has already been invested in blockchain (the transfer technology used by cyber currencies) startups.
The last time Bitcoin had a major spike in value it rose to $1,163 in late 2013 - but its value soon plummeted to less than $400 after a major exchange site was hacked.