For Americans still smarting from the 2008 financial crisis, the conviction of a big-fish investor for insider trading may feel like cold comfort. The recklessness of the financial industry helped bring about the recession; yet still almost no one involved has been punished. Contrast that with what has become a gusher of insider-trading cases. In the last 18 months, the government has brought charges against 47 people and convicted 36.

Raj Rajaratnam, found guilty by a jury this month on 14 counts of securities fraud and conspiracy, was the founder of the Galleon Fund, a now-defunct hedge fund once worth $7 billion. Prosecutors said he illegally used non-public information to gain an edge over other investors, completing trades that brought him an estimated $63 million. As long as such activities go largely unchecked, ordinary investors will rightly perceive Wall Street as a rigged game. (It is rigged, of course, for the benefit of the very rich, but one would hope there would be limits. . . .)

The last even roughly comparable spate of insider-trading cases came along in the 1980s, when money flowed into junk bonds and bets on takeovers. (Ivan Boesky and Michael Milken were among the fallen.) In recent years, the action has moved to hedge funds, which have created billionaires by the dozen. The great novelty in Mr. Rajaratnam’s case was the extensive use, for the first time, of wiretaps to prove insider trading. Once used mainly to crack down on organized crime, drug dealers and terrorists, wiretaps are now more likely to become a standard tool for fighting white-collar crime. Though it is too early to predict the overall deterrent effect, the word is definitely out on Wall Street.

Along with hedge funds, prosecutors are bringing welcome scrutiny to “expert networks,” a relatively new industry that helps facilitate investor research. Typically, these firms connect big investors with outside consultants. Prosecutors say some of these relationships foster illegal exchanges of information, and so far, they have charged about a dozen people. Six have pleaded guilty. Hedge-fund managers will have to look at these networks afresh and bolster their compliance programs to ensure that research does not shade into financial crime.

The integrity of Wall Street is important for the national economy. Perceptions that the playing field is even less level than most people think push out smaller investors and foster public cynicism, which can reduce investment capital. Huge amounts of money were pulled out of stocks during the financial crisis, and many investors have not returned. The Justice Department is right to crack down on insider trading. Even so, it does somewhat appear to be changing the subject. To really rebuild public confidence, it should ferret out wrongdoing in the financial crisis.

Just an FYI.Jim