It's no surprise that Apple secrets were so highly coveted. Check out the two-year chart.

A massive insider trading probe focused on expert networks illustrates just how valuable Apple's secrets--product road maps, new features, and forecasts--have become.

Yesterday, the feds arrested four people in an insider trading probe. According to the Associated Press, the U.S. government alleges that James Fleishman, an executive at Primary Global Research, used four consultants employed by public companies to deliver confidential information. The companies were AMD, Flextronics, Dell, and TSMC. The Holy Grail for traders looking to game the system, however, were details about Apple's plans via Flextronics, a contract equipment manufacturer.

The AP says a government complaint details how Primary Global Research clients were told about Apple's trade secrets including sales forecasts, new iPhone features, and a project known as K48, which became the iPad. The complaint was filed, but is sealed. There was an order to unseal the complaint on Dec. 16, according to the court's electronic filing system.

Read more of "Apple's stock surge makes its secrets a big target" at ZDNet's Between the Lines.