Investing.com - With Bitcoin and other cryptocurrencies seemingly under daily pressure, there's no shortage of influential voices sounding alarms. Even with the recent price correction, Goldman Sachs (NYSE:GS) declared cryptocurrencies in "bubble territory", saying the situation was worse than the dotcom boom of two decades ago and the tulip craze of the 17th century.Goldman predicted digital currencies will not "retain value in the long run"Noble Prize winning economist Joseph Stiglitz told Bloomberg that there will be no demand for bitcoin once it is regulated enough to prevent illegal activity.UBS Chairman Axel Webber told CNBC that his firm would advise retail clients not to invest in the currencies because they are speculative and risky.And the U.S. Securities and Exchange Commission dashed hopes of it approving crypto-based exchange traded funds anytime soon, saying it had concerns about volatility and liquidity.