“You’re a self-destructive doomsday machine!!”

The 80s had Chainsaw Al Dunlap; the Naughties have Carl Icahn. In either case, Rule #1 is: “Try not to get their attention!” If you do, Rule #2 is: “Do not piss them off!”

That’s exactly what Yahoo’s Jerry Yang and the Yahoo board have deliberately done. Carl, of course, is a major Yahoo stockholder famous for—unlike his predecessor Chainsaw Al—taking over corporate boards at underperforming companies, firing the CEO and turning the firm around (Al preferred dismemberment). Yahoo certainly qualifies as ‘underperforming’, unless you’re willing to spot them points for ‘doing as well as they can’ against the Google juggernaut.

A lot of ink has been spilled about Microsoft’s bid for Yahoo—which Icahn strongly backs—and their subsequent rebuff(s). According to the recently unsealed complaint in a shareholder suit filed against Yahoo, when Microsoft refused to go away Yang created a ‘poison pill’ to ward off further Microsoft incursions, “an ingenious defense creating huge incentives for a massive employee walkout in the aftermath of a change in control. The plan gives each of Yahoo's 14,000 full-time employees the right to quit his or her job and pocket generous termination benefits at any time during the two years following a takeover, by claiming a ‘substantive adverse alteration’ in job duties or responsibilities.”

Now that really pissed Carl off. In a letter to the SEC this week, Icahn pointed out that in its latest offer, Microsoft “had earmarked $1.5 billion of retention incentives (representing over $100,000 per employee) meant to allay any employee concerns.” Icahn’s best line: “Until now I naively believed that self-destructive doomsday machines were fictional devices found only in James Bond movies. I never believed that anyone would actually create and activate one in real life. I guess I never knew about Yang and the Yahoo Board.”

Icahn will clearly mount a major proxy fight to take over the Yahoo board, oust Yang and cut a deal with Ballmer. That loud thud was the gauntlet hitting the floor.