Seems like they want to allow it but are worried about laundering / being a bitcoin tumbler?

Afaik Robinhood is actually buying and selling coins on existing exchanges and baking any fees into the spread. For example, gdax doesn't charge any fee if you are a maker/using limit orders.

That means net as a population you can't sell, you can only buy. With that in place the price can only go in one direction.

All brokers sell order flow information. It's not a big deal, or even a deal at all.

How do you think they make money with a no commission service? Order flow has value.

One of the above, hence the question. (I assume the latter and that they’re just a marketing organization.) The scummy part is that their customers don’t know this.

What makes you think their customers don't know this? It's in their brokerage disclosure statement, same as anybody else who does this. It just doesn't... matter. Zero-fee transaction trading from my phone outweighs this.

It doesn't matter if money doesn't matter, yeah. Zero-fee transaction trading does not outweigh this, unless you have only peanuts to trade such that trading fees are more significant than spreads/execution.

avoid the spread by cross-checking and issuing a limit order. no fee on those, either.

Almost zero customers at any brokerage are aware of this - how many do you think read the fine print? It’s an unethical industry. And zero fee trading is great, except it’s not zero fee. But “stupid people deserve to get fleeced” seems to be enough ethics for most people.