Investing.com - Bitcoin is off to a rough start in 2018. Both its value and market capitalization are down sharply and its once formidable market share continues to shrink. Meanwhile, other currencies are gaining in stature because of the commercial potential of their blockchain technology.If that wasn't enough, Warren Buffett, the world's most famous investor, recently said he is almost certain bitcoin and other cryptocurrencies will "come to a bad ending."Given recent developments, it is not out of the question to look at bitcoin's survival prospects. Here are the five biggest threats. 1. Slower transactions.