Sony and Activist Investor Meet Politely For a hedge fund manager whose fame first came on writing invective-filled letters, Daniel S. Loeb's latest missive was a model of politeness. After a roughly two-hour meeting in Tokyo on Tuesday with senior management at Sony, the American billionaire handed a letter to the company's chief executive, calling for a shake-up of the electronics giant. However polite the note - Mr. Loeb says he wants to be a partner to Sony - it has started the biggest fight of the activist investor's career to date. Mr. Loeb's campaign is just the latest in a recent swell of corporate activism, as investors take on management at moribund companies and demand shifts in corporate strategy. Flush with cash from eager investors, these hedge fund managers are taking on ever larger targets. Companies as big as the Hess Corporation, Procter & Gamble and even Apple have found themselves in the sights of investors upset with what they see as waste and a disregard for shareholders" fortunes. In his 18-year career as a financial manager, Mr. Loeb has become one of the biggest stars in the world of hedge fund activists. His firm, Third Point, controls nearly $13 billion in assets and it was up 13.3 percent for the year so far through last week. Before Sony, Mr. Loeb's biggest target was Yahoo, where he waged a war to oust Scott Thompson as chief executive. Soon after winning that fight, Mr. Loeb successfully poached Marissa Mayer from Google to serve as the embattled Web pioneer's new leader. Since the investor first began agitating at Yahoo, the company's shares have soared 81 percent. "You can see Dan's fingerprints all over the turnaround," said Eric Jackson, a fellow hedge fund manager and Yahoo investor. He's brought an assurance to other Wall Street investors that there's an owner in the boardroom. That's what this company needed. A California native who began his career at the private equity firm Warburg Pincus and Citigroup, Mr. Loeb, 51, made his name through his investment acumen and the caustic humor often in his correspondence. Over the years, aficionados have collected his writings, from one executive's "imminent involuntary extraction" to another's "seemingly perpetual failure." Among his most famous epistles was his 2005 letter to the chief executive of Star Gas, a heating oil distributor. In 2,000 words, Mr. Loeb berated the official, Irik P. Sevin, for his "ineptitude" and for using the company as his "personal "honey pot." " "It is time for you to step down from your role as C.E.O. and director so that you can do what you do best: retreat to your waterfront mansion in the Hamptons where you can play tennis and hobnob with your fellow socialites," he wrote. Mr. Sevin resigned soon afterward. Mr. Loeb's aggressiveness extended beyond companies as well. His 2005 exchange with an applicant from Britain went viral around Wall Street for lines like "I love the idea of a French/English unemployed guy whose fund just blew up telling me that I am going to fail." That same year, Mr. Loeb battled with another hedge fund titan, Kenneth C. Griffin of Citadel, over poaching employees from other firms. "You are surrounded by sycophants but even you must know that the people who work for you despise and resent you," Mr. Loeb scoffed. The two have since become friends. As his success grew, Mr. Loeb branched out beyond activism into less confrontational strategies. Third Point reaped a $500 million profit last year by betting that Greece's government bonds would regain value after that country's debt crisis. He was also one of several investors to reap big gains from wagering on home loans after the financial crisis of 2008. And he profited from bets on bankrupt companies like Delphi, the auto parts maker. Mr. Loeb has had his share of stumbles as well. He fought for a seat at Massey Energy in 2006, deriding the coal miner for its inefficiencies and poor risk management. But he resigned a year later after his activist skills failed to lead to the ouster of Don L. Blankenship as chief executive and a sale of the company. The financial crisis also weighed down on Third Point in 2008, as the firm's main fund sank about 33 percent. Over all, however, Mr. Loeb retains the power to move stocks simply by revealing his presence. Earlier this year, he announced an 8.2 percent stake in Herbalife, a nutritional supplements company locked in combat with his friend and fellow billionaire, William A. Ackman. Third Point rode the subsequent rise in Herbalife's stock and sold out after a few months, pocketing an estimated $50 million profit. Among his recent big bets are Morgan Stanley, whose compensation practices he has admonished, and Murphy Oil, which he has said should consider shedding assets. The largest of these is now Sony, which he believes can trim its way to prosperity. It is likely to be a long campaign, especially given Japan's historic aversion to foreign interlopers. But Mr. Loeb appears to have won over at least a few fans for now. "We think Mr. Loeb's bold proposal bears consideration," analysts at Macquarie wrote in a research note on Tuesday, agreeing that a spinoff of the entertainment unit could propel Sony's stock by 60 percent. We recognize this latent value may indeed exist.