Raj Rajaratnam's remarkable journey from Sri Lanka to the heights of the hedge-fund world to felon ended Thursday when he was sentenced to 11 years in prison, the longest-ever term imposed in an insider-trading case.

In a defining moment for the government's campaign to stamp out what it describes as rampant illegal trading on Wall Street, U.S. District Judge Richard Holwell in New York said during sentencing that the billionaire investor's crimes "reflect a virus in our business culture that needs...