Anyone can vote in the Stock Stream Twitch Channel on which stocks should be bought or sold. Trades are executed automatically using Robinhood.

How much money is available?

The account is funded with $50,000 though unfortunately, due to FINRA/SEC regulations, trading will halt if the account value falls below $25,000.

Source: Stock Stream – Worlds First Multiplayer Stock Market Game Using Real Money

Unfortunately I haven’t found any figures about how well or badly this is doing