The S&P 500 SPDR ETF (NYSEMKT:SPY) fell 6.4% in the third quarter, and that decline led billionaire investors Warren Buffett, George Soros, and Carl Icahn to reconsider what they own in their portfolios.

After re-evaluating their holdings, all three of them sold off stakes in various companies, and since these investing icons have survived countless market corrections in the past, knowing what stocks they're selling could help you determine what names might be too risky for you to own, too. Let's take a look.

No. 1: Buffett breaks from Viacom
Warren Buffett's famous for his long investing time horizon, so it's particularly interesting when the Oracle of Omaha decides to sell off an investment, especially when that investment is Viacom (NASDAQ: VIA), a global media powerhouse.

Viacom makes its money by producing television and movie content distributed through traditional channels, such as cable companies, or next-generation content sources, including Netflix.

Previously, Buffett's belief that content producers had the upper hand in negotiating with content providers and advertisers led him to acquire more than 8 million shares in Viacom.

However, Buffett sold 2.6 million shares of Viacom in the second quarter and the remainder of his stake in Viacom in the third quarter.

Buffett's decision to walk away from Viacom occurred at the same time he upped his ownership in Liberty Media and Twenty-First Century Fox, the media giant run by the soon-to-step-down Rupert Murdoch.

Because Buffett's actions suggest he still has a penchant for media-content companies, his decision to sell Viacom may be company specific, and so it might be wise for investors to follow in Buffett's footsteps and consider owning other media companies, too.


No. 2: Soros bulldozes his homebuilding stakes
Billionaire hedge-fund guru George Soros uses a quick-fire investment style that means that the stocks he buys in one quarter could easily be sold in the following quarter. True to form, Soros punted 105 different companies from Soros Fund Management's portfolio in the third quarter, including three of the country's biggest homebuilders.

Specifically, Soros sold an $89 million stake in DR Horton (NYSE:DHI), an $80 million stake in Lennar Corp. (NYSE:LEN), and a $60 million position in Pulte Group (NYSE:PHM).

Soros' decision was made ahead of pending interest-rate increases by the Federal Reserve that could lead to higher rates on home loans and weigh down homebuying demand.

This week, Federal Reserve Vice Chairman Stanley Fischer reinforced investor conviction that the Fed will boost rates soon, when he made comments that appeared geared toward a possible rate hike in December, depending on global economic data.

If hawks are right that rates will increase, then companies like DR Horton could struggle to maintain their pricing power and boost the pace of their inventory turnover.

According to the National Association of Realtors, if rates were to increase by 1%, then a buyer would have to buy a home that costs 12% less to maintain the same monthly mortgage payment.

Although a lot of other things are considered when buying a home, a potential uptick in mortgage rates undeniably creates uncertainty across the industry, and therefore, it may not be a bad idea to rein in exposure to this group.

No. 3: Icahn pulls the plug on eBay
Carl Icahn is the most widely recognized activist investor in America, He tends to take really big stakes in a small number of companies to maximize his bargaining leverage.

One of Icahn's biggest bets in the past has been on eBay Inc. (NASDAQ:EBAY), the online auction retailer.

Icahn amassed a 46 million-share position in eBay in hopes of persuading eBay's board to spin off payment processor PayPal Holdings (NASDAQ:PYPL). At first, eBay bristled at the thought, choosing instead to highlight the benefits of a maintaining an integrated PayPal. Eventually, however, eBay concluded that PayPal's growth was indeed being stunted by its ownership, and therefore, it spun the company off in July.

With Icahn's work complete, it's not surprising that he sold eBay to focus on other opportunities. What may be more surprising, however, is that Icahn held on to his PayPal stake -- at least for now. Since PayPal remained in his portfolio, Icahn could think that opportunities to expand in mobile payments offer plenty of running room for PayPal in the future. And if that's true, then owning PayPal could prove profitable. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.