Everyone's got an opinion on buybacks, from executives andpoliticians to Twitter users. Now, in a year when it wasonce thought they'd reach $1 trillion, a louder voice is beingheard: the market's.

While the efficacy and even purpose of buybacks are the subjectof endless argument, if you believe they're meant to enhancereturns, lately they're falling short. Baskets of stocks with thehighest cash-return rates have been trailing the market in recentmonths.

Companies may have noticed; repurchase rates are falling. Maybeit's that valuations are stretched, though price-earnings ratioswere higher a few years ago. As for buybacks losing their bang,that could reflect changing tastes for how companies use cash.Anything from a growing preference for capital investment toaversion to piling on debt to pay for them.