Spin-offs are suddenly back in vogue in Corporate America, and on Wall Street. In the past week alone, at least four large companies announced plans to hive off some non-core assets and distribute shares of those companies to current investors.

Viacom Inc. stated this week that it is pondering plans to create a separate company from its MTV cable networks and Paramount film studio, leaving its television and radio operations with the existing company.

“We believe that a separation of our businesses into distinct and strong operating entities would allow us to optimize our capital structure and create unique investments that are more appealing to investors with different objectives,” said chairman and chief executive officer Sumner Redstone, in a statement. “Separately, these new publicly-traded entities could each pursue strategic paths that would maximize their long-term potential.”

Earlier in the week, Liberty Media Corp. announced that it intends to spin off a company comprising its interests in Ascent Media Group Inc. and Discovery Communications Inc. The transaction, which is intended to be tax-free to shareholders and Liberty Media, would create a new publicly traded company called Discovery Holding Co.

Also this week, Fortune Brands Inc. stated that it will spin off its ACCO World Corporation office-products unit, and that ACCO will merge with General Binding Corp., to create a supplier of branded office products with combined revenues of nearly $2 billion. In a statement, the company said that the spin-off “sharpens Fortune Brands’ focus on growing its high-return Home & Hardware, Spirits & Wine, and Golf businesses” and that the moves were designed “to enhance shareholder value.”

And Kimberly-Clark de Mexico SA, a Mexican pulp and paper goods company, announced that it intends to either spin off or sell its industrial products division, which accounts for 20 percent of its sales, according to Dow Jones, citing a filing with the Mexican Stock Exchange.

These spin-offs are no surprise to veteran watchers of Wall Street. In what has become a cyclical trend, fee-hungry investment bankers have gone through several phases of counseling companies to expand to non-core areas through mergers and acquisitions, only to advise them later to slim down when the deals don’t work out as well as had been hoped.

Now, even as merger mania heats up, companies that participated in the last M&A boom are moving in the opposite direction and shrinking to core, focused businesses.