Nothing ruins a CEO's day more than to have the administrative assistant say: "Carl Icahn on line one."
Activist investor Icahn disclosed in a tweet Tuesday that he has acquired a $1.5 billion stake in Apple and he considers the company "to be extremely undervalued." He also disclosed that he had spoken to Apple CEO Tim Cook that day.
Icahn, of course, is currently skirmishing with Dell CEO Michael Dell, opposing the executive's efforts to take Dell private. Icahn also has acquired stakes in speech recognition technology company Nuance and in Netflix.