I think judicious use of credit is a good strategy for growing your wealth, but when everyone is borrowing money for the same thing, something is up. Not everyone needs a margin account to participate in the stock market, for example.
Last I checked, brokerage margin accounts (in good standing anyway) are not included in FICO scores. Admittedly however, I have no knowledge of if or how a delinquent or otherwise unpaid margin debt may impact.