Why is most brokerages private? especially those futures brokers. I am looking to invest in some brokerage stocks (because most of my money goes there). And the only broker I know that trades publicly is TRAD (TradeStation). Then there are the $11 billion and $13 billion market cap Ameritrade, Et*trade etc. Anyway.. while we're at it, whats the business behind brokers? How many new accounts per year does it take to keep a 20% profit margin?