The cryptocurrency bitcoin has continued its stunning run-up, briefly surpassing the $3,000 threshold early Sunday afternoon.
That’s according to the CoinDesk Bitcoin Price Index, though competing index CoinMarketCap calculated the peak exchange rate at just a few cents short of $3,000 (bitcoin prices vary across exchanges, so different formulas can arrive at different exchange rates.)
The new peak continues a surge that began in earnest in early May, when a bitcoin was worth nearly $1,400. And it flies in the face of a widening consensus that the cryptocurrency market is in a bubble.
Get Data Sheet, Fortune’s technology newsletter.
That was Mark Cuban’s take last Tuesday, but the technology’s own central figures beat him to the punch by warning about overly inflated prices from the stage at the Consensus blockchain conference in May. And when he saw disgruntled attendees turned away from the overbooked Token Summit conference, Fortune’s Robert Hackett saw bubble written all over the bitcoin market.
Most observers, including Cuban, have by now accepted that blockchain technology, a promising innovation in data security based on shared ledgers, has huge potential for tracking assets and information in fields from supply chain management to health records. But the price of bitcoin is currently based in large part on speculation about growing adoption and innovative future applications. That’s even more true for parallel cryptocurrencies and blockchain systems like Ethereum, Dash, and Litecoin, which are mostly rising in tandem with bitcoin.
But a speculation-driven market is also an emotionally fragile market. If sentiment swings, it may swing quickly, and cause a lot of bitcon’s value to evaporate.
