We continue our Wall Street technology series with a look at high-frequency trading, where powerful computers can make hundreds of thousands of trades in milliseconds, making big money off tiny stock price differences. And password management company SplashData is out with its annual survey of the most common passwords. For the first time, a new terrible password is on top. The most common password is "123456," beating out the reigning champion, which is just "password." Either one is a fine invitation to get hacked.