Companies just can't stop buying back their own stock.

And they're not just buying a few shares. Often, company buyback billions of dollars of stock.

Apple (AAPL - Get Report) recently bought back $20 billion of its stock, part of a $100 billion share buyback program. Qualcomm (QCOM - Get Report) , a chip maker, is set to buy $10 billion of its stock in the next month.

Stock buybacks are great for shareholders. Think about it: if a company buys it's own stock, that reduces the number of shares available on the market - which increases the price of the stock. It's simple supply and demand.

The money companies are spending on buybacks could be spent on growing the organization and hiring more workers. That's why some experts worry that the pressure for public companies to keep their share prices elevated - by buying their own stock - is hurting the economy in the long run.