Robinhood stock trading app valued at $1.3B with big raise from DST

Irrelevant, because for someone who knows what they are doing in the stock market paying $10 or $0 per trade is not going to save them any money.

Dangerous, because it promotes more trades for the “unsophisticated” investor and encourages leverage = very dangerous situation.

Bottom line, if you do not know what you are doing, don’t do it, buy and hold is not a strategy and sooner or later will leave you very disappointed, especially if you are leveraged on top of that. Just ask the investors in the Japan asset price bubble when they’ll see the top again – looks like never in their life time...

To be able to invest successfully you need to spend the time and educate yourself like in any other profession or hobby and the first step is to go to eBay and search for historical stock market data, you can buy 20 years of data for less than $100 and you can test all your ideas for free and without losing a single penny...

Good luck!

The second to last paragraph seems to me to be quite dangerous. I'd wager it is quite likely a person would see a pattern that really isn't there.

http://www.ebay.com/usr/artinvest389

I did test random samples from the data against other data providers and I am using it every day an yet to find errors or mistakes...

No, I am not talking about both limit orders and market orders. I am talking about nearly all orders that a retail trader would use. As an institutional trader, you would sometimes use orders that will be filled at worse prices than the lit market. Retail traders do not typically have a need for those orders.

> Unless you have full access to all order books you can't really know whether you were filled at the best price of all lit exchanges.

This is true, but the person filling your order does have a responsibility to ensure that your order is filled at the lit exchange price or better. If you find contrary evidence,the regulators would possibly be willing to pay you a lot of money for it.

> Though the "loss" might be insignificant for the average retail investor trading very liquid instruments.

Compared to trading on a lit exchange, you should not be experiencing a loss and you are possibly experiencing a small gain.

You might be experiencing a small loss compared to trading through a broker that sends your orders to HFT firms, but does not accept payment for order flow. I would be interested in seeing data on that, but I would very surprised if that were true.

According to your Schwab link, if there is no fill improvement on Robinhood then you are better off using Robinhood for orders under 500 shares because commissions are $4.95 and the fill improvement is less than that. Is that your interpretation as well? Do you have a link showing that Robinhood customers do not get any fill improvement?

I don't think the KCG link is relevant as they do not have retail customers. This means that KCG's customers are going to be more informed than Schwab's customers so you can't afford to give them as much fill improvement.

From what I've read in this thread that seems to be Robinhood's target market.