The author picks on Apple, but doesn't mention that Apple has dramatically increased its headcount and R&D spending all the while buying back stock. The truth is Apple is a mature company that is an incredible money making machine, they literally don't have ways to use the profits to make more successful tech products. What else should they do other than reward shareholders?
Anyway, if it turns out when I sell my shares they were bought by the company, guess what I'll do with the proceeds? Either spend it (stimulating the economy) or plow it back into other investments. Buyback money doesn't magically disappear, it just cycles what the capital is being used for.