I'm not certain, but I think coinbase is the main custodian for all the big corporate entities. I think the fact that it is a public company supposedly adds credibility. 

brandonsbytes

bitcoin

What do you think of Michael Saylor’s “sell debt, buy bitcoin” method?

Because it's a publically traded company, it has been given a valuation premium above the fiat value of the bitcoin it "owns." (If you trust coinbase). It is a toy for hedge funds to play with volatility. How long Saylor can keep all the balls in the air is anyone's guess. 