We’re in a stock buyback binge. Companies are tripping over themselves to repurchase their own shares this year, and most investors see this as a bonanza.

But not all of these buyback programs wind up benefiting shareholders. In fact, some can be quite costly and destroy value rather than create it.

On the positive side, companies that buy back shares reduce the amount of stock they have outstanding. This has the effect of increasing earnings per share and the stakes of existing shareholders. That’s why many investors have been pushing for buybacks, especially at companies sitting on mountains of cash.

Such calls are being heeded. April was the biggest month ever for buyback announcements — $141 billion, according to data compiled by Rob Leiphart at Birinyi Associates. If these buyback plans continue at the current rate, they will reach $1.1 trillion this year, he said, well above the peak of $863 billion in repurchase announcements in 2007. In April, Apple and General Electric announced $50 billion programs. In February, Home Depot said it would buy back $18 billion of its stock, and Gilead Sciences chimed in with a $15 billion plan. Also in February, PepsiCo announced a $12 billion program.