When companies merge, executives and shareholders alike often get excited. But not every big corporate transaction works the way everyone hopes it will.

New York Times (NYSE:NYT), struggling in this age of fading newsprint, aims to sell The Boston Globe, which it bought in 1993 for $1.1 billion. Worse still, it might turn around and sell the Globe for less than $100 million, resulting in a whopper of a loss for Times.

Need more proof that mergers don't always pan out as planned? Just ask shareholders of Time Warner. Time Warner merged with America Online, and investors have largely suffered ever since.

Customers can suffer, too. When they do, shareholder suffering may follow. Some critics fear that Amazon.com's (NASDAQ:AMZN) recent purchase of Zappos will threaten the online shoe-seller's famous focus on customer service. Then again, Amazon's record on helping customers isn't too shabby, either.

Acquisitions aren't all bad
Some companies don't just make occasional buys -- they run on acquisitions. Johnson & Johnson, for example, is famous for buying smaller companies, among other frequent purchases. In 2006, it bought Pfizer's (NYSE:PFE)consumer health unit for nearly $17 billion, adding names such as Listerine, Visine, Neosporin, and Lubriderm to existing brands such as Band-Aid and Neutrogena. Other companies that have historically grown through serial acquisitions include Cisco Systems (NASDAQ:CSCO), eBay (NASDAQ:EBAY), and Procter & Gamble (NYSE:PG).

Warren Buffett's Berkshire Hathaway (NYSE:BRK-B) is always on the lookout to buy another company, and he prefers swallowing his targets whole to simply buying a piece of them. True, not every purchase has been a financial winner; Buffett, in what he dubbed his worst deal ever, traded 1.6% of his company for Dexter Shoe in 1993, a stake that would be worth more than $2 billion today. Still, his successes, such as GEICO and See's Candies, have more than made up for his failures.

Not every merger will pay off -- but by the same token, not every deal will be a dud. Just steer clear of companies engaging in obviously silly or reckless deals. Executives chasing the thrill of an acquisition, without regard to good sense, may prove less than savvy in other areas of management as well.

Get the latest news on Warren Buffett's purchases and sales. Morgan Housel's done all the work for you right here.

Longtime Fool contributor Selena Maranjian owns shares of Johnson & Johnson, Time Warner, Procter & Gamble, Berkshire Hathaway, and eBay. Amazon.com, Berkshire Hathaway, and eBay are Motley Fool Stock Advisor selections. Johnson & Johnson and Procter & Gamble are Motley Fool Income Investor recommendations. The Fool owns shares of Procter & Gamble and Berkshire Hathaway. Try any of our investing newsletters free for 30 days. The Motley Fool is Fools writing for Fools.