The story has since been pulled from CNN's "iReport" Web site, but not before sparking an online firestorm and (temporarily, at least) putting a dent in Apple's stock price.

Silicon Alley Insider has a screenshot of the subtle headline—"Steve Jobs rushed to ER following severe heart attack"—that appeared on the iReport home page Friday morning.

Apple PR quickly denied the story, and CNN eventually yanked the story (posted by a certain "johntw") from the site—but not before Apple's stock suffered a sharp (if temporary) dip, while online message boards and Twitter feeds went nuts over the rumor.

The false story comes a little more than a month after Bloomberg accidentally sent an unfinished obituary for Jobs over the wires. That was a publishing error, however, while the iReport story was clearly a prank at best, a malicious lie at worst.

Meanwhile, CNN is going to have to do a little soul search over its iReport policies—or, apparently, the lack thereof.

Now, false stories appear on sites like Digg pretty regularly—but most readers know to take Digg submissions with a grain of salt (and alert Digg users are good at quickly flagging suspicious stories that hit the home page).

But as the Insider points out, iReport has CNN branding all over it, which implies some level of authenticity—or at least enough to send Apple's stock price over a cliff after the "heart attack" story got posted. (CNN does have an iReport disclaimer—"The views and content on this site are solely those of the iReport.com contributors. CNN makes no guarantees about the content or the coverage on iReport.com!"—but it's in the iReport FAQ, not the home page.)

In any case, looks like CNN (and other members of the MSM, for that matter) should be thinking twice before getting into the "citizen journalism" business.

Related:
Apple Denies Steve Jobs Heart Attack Report: "It Is Not True" [Silicon Valley Insider]