“Wall Street analysts have been left bewildered,” writes Susan Pulliam in Wednesday’s
Wall Street Journal
, “as federal prosecutors begin to home in on insider-trading cases that appear to involve routinely published information about public-company supply chains.”

Case in point: Apple (AAPL), a hot stock with an unusually secretive corporate culture. Today, dozens of analysts and so-called expert networks compete for every scrap of information about Apple that might affect the stock’s performance.

Now one of their favorite tools — calling on (and perhaps paying) sources who work for the company’s suppliers — is in the spotlight.

Fueling analyst concerns is the definition of insider trading that former SEC chairman Paul Atkins gave the Journal:

“Insider trading basically comes down to where you know or ought to know that the person from whom you’re getting this information has a duty to someone else to keep it confidential. If you go in and pay the mail clerk to give you special information, that’s not proper.”

The Journal article singled out for special mention a Nov. 12 note to clients by Rodman & Redshaw’s Ashok Kumar that suggested, based on “supply chain checks,”  that iPad sales might fall short of expectations this quarter. That note — which we reported on here — helped spark a one-day run on Apple that shaved nearly $8 billion off its market cap.

The Journal did not say or imply that either Kumar or his firm was under investigation.

[Follow Philip Elmer-DeWitt on Twitter @philiped]