The latest 13F season has arrived, when many money managers issue required reports on their holdings. It can be worthwhile to pay attention, as you might get an investment idea or two by seeing what some major investors have been buying and selling.

For example, consider SAC Capital Advisors, run by Steven Cohen. SAC is one of the biggest hedge-fund companies around, with a reportable stock portfolio totaling $17.2 billion in value as of June 30, 2013. A company doesn't generally grow that large without performing well, and indeed, Cohen has reportedly averaged returns of roughly 30% annually over two decades.

How did the hedge fund achieve its success? Well, perhaps via some insider trading. Foul play has been alleged, and the company pled guilty late last year to charges of wire fraud and securities fraud, agreeing to pay a record settlement. The company is looking into changing its name now. While you might not want to consider the managers of SAC as your ethics heroes, it's not crazy to keep an eye on their investments.

SAC Capital Advisors' latest 13F report shows that it reduced its holdings in Micron Technology, (MU 2.67%), eBay (EBAY 1.16%), and Nokia Corporation (NOK 1.13%).

Micron Technology recently reported a strong first quarter, with revenue surging 120% and earnings popping 165% over year-ago levels. Micron's purchase of the Japanese company Elpida has been a game-changing move, turning Micron into the world's second-largest DRAM maker with twice its previous memory capacity, more pricing power, and more production facilities, as well. With demand growing for solid-state drives, bulls like the company's investments in NAND memory technology. At an analyst conference, management said it was focused on "operational excellence and deployment of advanced technology," as well as decreasing debt, among other things. It stopped paying a dividend in the 1990s, but with its current strength and growing profit margins, some would like to see the payout reinstated. Meanwhile, some wonder whether the company might be acquired by a bigger technology company such as Intel or Apple.

Vast online marketplace eBay reported a strong fourth quarter last month, with revenue and earnings up 13% and 16%, respectively, over year-ago levels. More recently, it announced a promising investment in a major Indian online marketplace, positioning it for possible significant growth down the road. Meanwhile, activist investor Carl Icahn has been agitating for eBay to spin off its highly successful PayPal business (which generates about 40% of its revenue), though many think the marketplace and transaction businesses work well together. Bulls love eBay's light business model and double-digit net margins -- though those margins have been shrinking a bit in recent years. Its free cash flow is sizable and growing, though.

Finland-based Nokia has surged more than 70% over the past year, in which it sold its handset business to Microsoft (MSFT -0.01%). (Nokia recently released its X smartphone, which runs a modified version of Android, and investors are waiting to see whether Microsoft keeps or kills it.) Meanwhile, the new Nokia features operations in mapping, networking, and more, along with lots of patents. After releasing mixed fourth-quarter results, management maintained optimism, with the chief of networking noting that "we are seeing excellent momentum in Greater China where we believe we are on track to become the leading foreign vendor."