Xapo’s billionaire backers include LinkedIn Corp. co-founder Reid Hoffman and former Wall Street trader Mike Novogratz, who’s in the process of setting up his own cryptocurrency merchant bank. Their bet is that Bitcoin is here to stay, and so is its biggest scourge, theft. The first rule of owning Bitcoin is to securely keep your private key -- the code that lets you spend your coins. If thieves get it, they can loot your holdings in an instant, with no hope of recovery. Putting keys on a device connected to the Internet is both convenient and perilous: Hackers have proven adept at obtaining them from afar.

https://www.bloomberg.com/news/articles/2018-05-09/bunkers-for-the-wealthy-are-said-to-hoard-10-billion-of-bitcoin