"My work here is done". Daniel Loeb sells Yahoo stock. Shares falls by five per cent.

Last year Mr Loeb was instrumental in forcing the resignation of Yahoo's CEO, Scott Thompson, by exposing that Thompson had "embellished" his CV by claiming to possess a computer science degree that did not exist. Mr. Thompson was at the helm for just four months before resigning "on health grounds".

So, exit one very short-term CEO and enter another who has now lasted a whole year: Mr.Loeb was also a prime mover in poaching Marissa Mayer from Google and overseeing her installation as Thompson's successor.

However, Mr. Loeb's primary responsibility is to his Third Point hedge fund and he has now judged it to be the time to sell-off 40 million Yahoo shares. He bought them for about $13.50 apiece and is selling them back to Yahoo at $29.11. A nice little earner, as they say, at a profit margin of 124 per cent. Yahoo's stock fell by five per cent as the news percolated through the markets.

Daniel Loeb will, for now at least, retain 20 million Yahoo shares and embattled Yahoo CEO Marrisa Mayers is claiming that by retaining an interest in the company, Mr. Loeb is, in fact, giving it (and her) a vote of confidence for the future. However, many Wall St. analysts have opined that his resignation from the Yahoo board is indicative of his concern and belief that Yahoo's shares have peaked and that, long-term, the company is a busted flush.

And beneath the fake smiles and spurious bonhomie Ms. Mayer must be worried that now Loeb has bailed other big investors will follow suit. Until today Yahoo shares had been surging but Daniel Loeb's decision to sell indicates that he thinks that surge is about to lose momentum. Indeed, his actions have already stalled it and that may be a signal for others to get out whilst the going is comparatively good.

Next on Mr. Loeb's hit list is Sony. He owns seven per cent of the company and has been agitating for a spin-off of Sony's entertainment business assets. There's another quick profit to be made there and the suits at Sony must be rather concrned this morning.

Meanwhile back at Yahoo, Marrisa Mayer issued a statement saying, “Daniel Loeb had the vision to see Yahoo for its immense potential - the potential to return to greatness as a company and the potential to deliver significant shareholder value.”

Well, Daniel Loeb certainly saw the potential of a quick and profitable flip when he bought into Yahoo. That's not to say though that he thinks that Yahoo can "return to greatness" in the future. Indeed, the odds seem to be stacked against that possibility. There is, as yet, no evidence that Yahoo can change quickly enough to be able properly to compete with the new breed of tech companies and social media sites that now dominate the heights Yahoo used to call its own.

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