Feb. 15--Corporate America's love affair with its own stock has come to an abrupt end.

In yet another sign of bad times ahead, public companies nationwide and in Minnesota are pulling the plug on massive share buyback programs that were once seen as a way to boost share prices.

This week, 3M Co. joined a parade of large companies -- from Target Corp. to General Electric -- that have stopped repurchasing their own shares in order to preserve cash in uncertain times. Nationwide, stock buybacks by Standard & Poor's 500 companies plunged 48 percent to $89.7 billion in the third quarter after hitting a record $172 billion the previous year. Fourth-quarter figures were not yet available.

The pullback brings an unprecedented, five-year boom in stock buybacks to a close, and raises new questions about whether these programs were really the best use of excess cash. Some argue that much of the tens of billions of dollars spent buying back shares should have been used to develop new products, buy more efficient machinery or be returned to shareholders in the form of dividends.

One lesson from the economic downturn of the past year is that monster buyback plans are a poor indicator of a company's financial health. A number of companies that announced buyback programs in 2007 -- including AIG, Merrill Lynch, Lehman Brothers and MoneyGram International -- have either failed or been rescued. Others have seen shares plunge since unveiling their buyback plans.

Indeed, investors are beginning to treat huge buyback announcements with skepticism -- one reason companies are scaling them back or canceling them entirely, said Howard Silverblatt, who tracks stock repurchases for Standard & Poor's. "No one believes you can fight the market with a buyback," he said. "It's like trying to hit a cement wall with your fist. The market's too big."

Share buybacks have been around for decades, but they gained in popularity after the bear market of 2001 as a way for companies to entice shareholders with the promise of better returns to come. Buybacks reduce a company's outstanding shares, so they can bump earnings-per-share.

Previously, the mere announcement of an aggressive repurchase plan generated a bounce in a share price, and management teams liked their flexibility. If they scaled back or suspended the plans, investors didn't react as harshly as if they had canceled a dividend.

Over time, as profits improved and companies built stockpiles of cash, buybacks gradually displaced dividend payouts.