REFILE-FACTBOX-Bitcoin's famous backers
(Refiles to change slug, no changes to text) Feb 16 (Reuters) - Bitcoin rose above $50,000 on Tuesday for the first time, continuing a rally that has seen it rise nearly 900% since March last year. Sceptics of the cryptocurrency’s ability to go mainstream say it is rarely used for regular transactions and is too volatile to be a reliable store of value or hedge against inflation. But it has attracted endorsements from business people, celebrities and companies, betting bitcoin will become an alternative to central-bank issued currencies. Here are some of bitcoin’s best-known backers: Elon...