I'm with you ethagknight. Look at my comment below. I think it's a different ballgame at these prices, counting even more on coinbase that they are doing the rational things.
I find this hard to believe that coinbase is doing this with no regulation. I don't know if you all saw what happened to Full Tilt Poker, look it up. I'm afraid something like that could happen to coinbase. FTP got an influx of deposits and used that to fund players for when they withdrew. FTP was using the fund pool for other reasons and pocketing some of it, while still being able to payout players. The day came the gov't shut down the site but the company did not have the funds to pay back the players.
Now this might be different because bitcoin is what it is this is, while you control your wallet and this occurs more like a stock market rather than full tilt poker. Still I'm somewhat skeptical because coinbase could be doing something more complex to where they take on risk. Just my opinion, have to research more but this is a thread I was looking for.
If you look right now at both Bitfinex and GDAX/Coinbase, there is a $1000 discrepancy in price between the two. I know that these are separate markets, but they both represent bitcoin, and I wish I knew how to arbitrage between the two if a Bitcoin is a Bitcoin the world over.. My guess is that is exactly what Coinbase is doing: showing its exchange price, but executing sale orders on different exchanges.
