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We should never blindly copy any investor's moves, no matter how famous, talented, or successful the investor. Still, it can be useful to keep an eye on what smart folks are doing. 13F forms can be great places to find intriguing candidates for our portfolios.

For example, a glance at the latest quarterly 13F filing of Paulson & Co. shows that it closed its position in General Motors Company (NYSE:GM), selling more than 4 million shares -- a stake worth more than $130 million today.

Why pay attention to Paulson & Co.?
If you're wondering why we should care what Paulson & Co. is doing, know that it's one of the world's largest hedge fund companies, with a reportable stock portfolio topping $23 billion in value as of June 30, 2014. Founded by John Paulson in 1994 and owned by its employees, Paulson & Co. has specialized in merger arbitrage, among other things, profiting when one company buys or merges with another (or merely announces plans to do so). It has grown into one of the largest hedge fund companies in the world.

Paulson was behind "The Greatest Trade Ever," seeing the housing market's collapse coming before many others and betting against subprime mortgages. (He's not the only such investor selling shares of General Motors.) According to GuruFocus.com, Paulson more than doubled the S&P 500's return over the 15 years through 2011, and according to Paulson in 2012, he had only two years with losses in the past 18 years. His performance has faltered in recent years, though, in part due to a heavy position in gold.

Why sell General Motors?
So why would Paulson, or anyone, sell shares of General Motors? The company has been turning itself around since its bankruptcy restructuring in 2009. But there's one big problem most interested investors are focusing on: its massive recall debacle. It's not yet clear how much its recalls will cost (my colleague John Rosevear has suggested $6 billion, which includes lawsuits) and whether the company will face criminal charges as well. Of the 37 million recalls issued by U.S. automakers this year, about two-thirds came from GM.

Other concerns include net profit margins and net income trending downward while debt is high and rising -- though revenue has also been rising and free cash flow is robust at roughly $5 billion annually. Taken together, those details make General Motors far from a slam-dunk investment, but a growing top line is hugely valuable, suggesting that earnings can grow once operations get more efficient.

The drawbacks of General Motors may lead investors to turn to other automakers such as Ford Motor Company (NYSE:F), but despite its own recent successes, Ford is carrying much more debt than General Motors and has recalled millions of vehicles, too. It's also been ramping up its substantial incentive discounts on vehicles.

Why buy General Motors?
Here's a funny thing: Despite General Motors' massive recall, its sales are up. In fact, in part via a $500 incentive, it's getting many owners of recalled vehicles to buy new ones. Its July sales report was very strong, featuring double-digit growth. Its recent vehicle redesigns have been effective, and more are coming.

A key area of promise for General Motors (and other automakers) is China, and General Motors leads the pack there, investing heavily in further growth. (Note, too, that it's among the automakers being investigated in a Chinese antitrust probe.) It's also making significant investments in other populous developing markets, such as Brazil.

Then there's its newly reinstituted dividend, recently yielding a meaningful 3.3% and likely to rise over time. Many also see promise in new CEO Mary Barra, who has been with the company for more than 33 years in many capacities.

Overall, while General Motors is indeed facing some challenging times, long-term investors should consider it for their portfolios. Its price-to-sales ratio was recently 0.4, well below the industry average, and its forward P/E ratio is below eight. Warren Buffett, a legendary value investor, has more than $1 billion in GM stock, and he added nearly 3 million shares in the last quarter.

Longtime Fool specialist Selena Maranjian, whom you can follow on Twitter, owns shares of Ford. The Motley Fool recommends Ford and General Motors. The Motley Fool owns shares of Ford. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.