Without a doubt, cryptoexchanges are wildly profitable. Bitcoin is seeing 200K plus transactions a day. If you assume Coinbase has a very conservative 10% of the market, you get 20k x 7 = $140,000 in just BTC fees (not including the cut they take in the trading price or the other transactions). To your point though, the lack of regulation is most worrying in that there's no official backing or support for our deposits. Hopefully, some will start to insure their exchanges with their profits.