Volatility be damned—a '90s icon makes a risky comeback.

TD Ameritrade, another brokerage popular with active traders, is seeing record levels of trading activity, according to representative Kim Hilyer. New assets for the first 20 days of October were approximately $2 billion, compared with $2.8 billion for the entire fourth quarter.

"Traders are taking advantage of the volatility in the markets-making more intraweek and intraday trades than we've seen before," Hilyer says. "Clients are not quitting their day jobs en masse to trade full time, but we are seeing casual traders becoming more active."

TradeStation, another firm that markets itself to high-volume investors, reported record net revenues of $41.8 million in the third quarter. The company's brokerage commissions and fees increased 22 percent year over year as a result of higher trading volume by the brokerage firm's client accounts, due mainly to increased market volatility and net account growth, according to SEC filings.

"High volatility means you have a lot of ups and downs in the market, and that allows you to trade," says CEO Solomon Sredni. "When the market is flat, there isn't as much opportunity."

Study after study shows the vast majority of investors, even professional ones, are unable to beat the market averages. For that reason, day trading is often derided as gambling by financial advisers and their ilk. You might be in the black for a while, they say, but eventually you're going to lose big.

Marshall Rockwell, a day trader in Los Angeles, was aware of the risks, but in October he decided to try his hand at trading stocks full time.