A way to fool investors into thinking company is doing well and hit the management internal target for stock option.
Something like that; a correct financial operation at best; for exemple, Lehman Brothers was buying back its stocks before collapsing
From a total return perspective, companies are as bad timers as the average investor. Mergers and Acquisitions tend to peak with markets too. Both indicate exhaustion of profit opportunities in the broad economy.
http://blogs-images.forbes.com/jessecolombo/files/2014/07/buybacks.pngEDIT: sgbett beat me to it.
