Share buybacks are an alternative to dividends for returning value to shareholders. They can be a hugely valuable tool. AutoZone (AZO 0.99%) and General Motors (GM 0.77%) are two companies that have absolutely crushed it with share buybacks.When bad is goodUnless you're familiar with AutoZone as a company and a stock, it might seem a little backward to you. After all, what's bad for your average car owner is actually good for AutoZone and its shareholders. When consumers have a car problem, they can buy the ...