The latest 13F season is here, 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 Paulson & Co., founded in 1994 by investing giant John Paulson. Owned by its employees, the company 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 & Co.'s latest 13F report shows that it has shrunk or eliminated its positions in American Capital Ltd. (ACAS), MGM Resorts International (MGM 0.59%), and Vodafone Group Plc (VOD -0.54%).

American Capital Ltd., a private-equity and venture capital firm specializing in buyouts and recapitalizations, has been in "near-liquidation mode," selling off some of its investment portfolio as it shifts its business model in order to create reliable income streams from money management. Its last quarter featured lower revenue and earnings than the year-ago quarter, with costs rising. Some are hopeful of a possible spin-off, while others see executive compensation levels as excessive.

MGM Resorts International has bulls excited about its double-digit growth rates in recent years and its plans to double its capacity in the hot gaming market of Macau. Better still, the company is doing well in China, is looking to expand in Japan, and is positioned to do well in Las Vegas, which is expected by some to soon become a hot market again. Bears, though, note its heavy debt load, recently near $13 billion.

Since U.K.-based telecom titan Vodafone Group sold its remaining stake in Verizon Wireless to Verizon for $130 billion, it has been acquiring telecom businesses in Spain, Germany, and India. Vodafone should profit from Europe's rebounding economy, but some wonder whether it's spending too much on acquisitions, while others wonder whether Vodafone itself will be acquired. Bears would also point out deteriorating numbers in its financial reports, as they question the wisdom of shareholder-pleasing dividend hikes. On the other hand, the stock does offer substantial free cash flow, a generous dividend (recently yielding 7.2%) that seems sustainable for now, and a seemingly cheap stock price.