Carl Icahn moves stocks with tweets now.

Yesterday Icahn tweeted that he had taken a position in Apple. The stock immediately was bid upward.

This much is clear: we're living in the golden age of activist investors.
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Icahn was once frequently called a "corporate raider."

Gordon Gekko, the villain of Oliver Stone's "Wall Street," was in part based on Icahn. In the film, Gekko plots to take over an airline that he secretly intends to dismantle. Icahn took control of TWA, sold off some of its most valuable assets, and ushered the company into bankruptcy less than a decade after gaining control.

Icahn never liked—actually viscerally hated—the term corporate raider. And that phrase has mostly been banished to the ash heap of history.

Icahn now almost universally is referred to as an "activist investor." He is considered the godfather of activist investors, some of whom half-jokingly call him "Uncle Icahn."