ChainCatcher news, Greenlight Capital founder and billionaire David Einhorn expressed his skepticism in a recent letter to investors, stating that digital assets are approaching dangerous levels of speculation.Einhorn wrote, "Nothing is stopping the launch of more tradable tokens, and no one knows what will happen next, but it feels like it will be crazy. More likely, level-headed governments should not borrow trillions from the bond market to engage in Bitcoin speculation; in fact, doing so makes no strategic sense." Einhorn also criticized some bullish predictions that pushed Bitcoin to historic highs.In the letter, he stated that Greenlight Capital has established short positions in two leveraged ETFs related to MicroStrategy, the largest corporate holder of Bitcoin.Einhorn stated, "These products are destined to fail. We know who the President of the United States is, but no one can guess what he will do." He also mentioned that economic policies, tariffs, and Trump's mission to cut government spending make the outlook even more uncertain.