Shareholders were spooked about a new threat to the company's core business; a fresh dividend declaration didn't help.It can be scary when a major blue chip company comes for your business. This was a significant factor behind the nosedive in Walgreens Boots Alliance (WBA -0.11%) stock over the past few trading sessions. Week to date as of Friday before market open the company's share price had tumbled by more than 13%, according to data compiled by S&P Global Market Intelligence. Even Walgreens' maintenanc ...