A key reason for bitcoin's dominance in the nefarious online underworld, say technologists and cybercrime experts, is its size - the total value of all bitcoins in circulation is more than twice that of the nearest of hundreds of rivals. Also, a big part of bitcoin's recent surge is the increase in demand for other digital currencies being sold in so-called "initial coin offerings", or ICOs. Under ICOs, blockchain start-ups sell their tokens directly to the public to raise capital without any regulatory oversight.
"Bitcoin up 100 percent in under 2 months. Shanghai down almost 10 percent same timeframe, compared to most global stocks up. Probably not a coincidence!", Jeffrey Gundlach, chief executive at DoubleLine Capital tweeted on Tuesday. Strong demand for bitcoins in Japan has also fueled the rise of the virtual currency that can be moved like money around the world quickly and anonymously without the need for a central authority.