For 1 they are just doing the next round of fund raising with a 1 billion valuation and will be raising around 100 million. 2 they take pretty hefty fees for buying and selling coins. 3 they are linked to exchanges. 4 they have there own reserves of cash and bitcoin what will be rising in price aswell so I don't think they are short of cash lol. This is a quote from coinbase "We integrate with a variety of exchanges and also hold our own reserves. When you sell your bitcoins for USD we usually sell them to other Coinbase users at some point down the line (this is where our reserves come from), but we may cash them out if needed. In general, our goal is to abstract away some of the complexity so it's a simpler process for our users. What we have now is a good start but not finished by any means. Hope it help". So please don't post false information on here about things you know nothing about and do some research first....