Don't forget the payment processing companies Coinbase and BitPay. Despite Bitcoin being an open and transparent system, we have no idea how many coins transfer hands unfortunately.
I recall them saying that they processed 100 million USD in payments in 2013. No idea how they are doing now.I wonder how much of that is actually purchasing concrete goods and services. Do people use Bitpay/Coinbase for online gambling? Do people use them, instead of the exchanges, to turn bitcoins into dollars? (Just register with them as a merchant and but a Nothing from yourself in BTC, have it delivered as dollars?)