The great depression was largely the result of massive numbers of everyman speculators entering the markets with reckless amounts of leverage. Robinhood vastly lowers the barrier for gambling with money you don't own. There's a reason you can't buy lottery tickets with credit cards.
There are much better options for high-risk (reckless) trading, like 500x Forex accounts, "binary options", and lots of other nonsense enabled by offshore jurisdictions.
For an easy example of how reckless/risky these alternatives are, look at FXCM/Alpari/etc after the 2015 EURCHF action.
500:1 leverage sounds so crazy I wouldn't be surprised if it's used as a money laundering vector.
Next, forex markets are so heavily traded they have a virtual guaranteed stop. That is, if you set the order you will get it filled no worse than that price.
The only way a broker gets hit is a sudden currency drop, like the Swiss franc did a few years back.
The Great Depression is a lot more complicated than Black Thursday... (inflationary monetary policy during most of the roaring 20's, contractionary policy during the market crash causing bank runs).
Well. You can.
Not sure what you were trying to say.