Buybacks are at record levels.  Historically, buybacks have not always been good over the long term, specially if the buybacks continue well past the point fair valuation for the company.  Then we have those companies whose executives use the strategy as a personal piggy bank.  

Then there is the cyclical nature of economies, what seems cheap one moment can look down right expensive in a different economic and/or interest rate environment.

That said, there are companies that have traditionally done quite well in managing how and when to do share buybacks, but they are not the majority.