Bill Gates said that if he could do this, he would definitely bet against bitcoin, calling the cryptocurrency one of the most speculative things in the world. This is reported by CNBC.
As an asset class, you're not producing anything and so you shouldn't expect it to go up. It's kind of a pure 'greater fool theory' type of investment. I agree I would short it if there was an easy way to do it. Bitcoin and ICOs, I believe completely [they're some] of the crazier, speculative things.
The theory of a greater fool claims that you can make money buying securities, regardless of their quality, whether they are overpriced or not, and sell them later with profit because there will always be someone ("greater fool") who also expects to resell quickly the asset with a profit. That's why, the theory claims, speculative bubbles are growing, which are sure to burst, bringing down the prices in a massive sale.
Like many critics of the cryptocurrency, Gates said the underlying blockchain technology had its advantages.