Amazon wiped out $17.5 billion from eight companies' market values Thursday with just two announcements.

The e-commerce giant has become a force on Wall Street. Even a hint it might take on a new industry can send investors running and stocks tumbling. That was evident Thursday.

Amazon said it would recruit entrepreneurs to run local delivery networks, a move that could divert business from carriers FedEx and UPS. Together, the two companies lost nearly $3 billion in market value on Thursday, with UPS bearing the greatest losses.

A few hours after that announcement, Amazon said it would acquire online pharmacy startup PillPack, a deal that's already shaking up the health-care industry. Sources told CNBC that Amazon paid roughly $1 billion for the company. News of the deal erased about $14.5 billion from drugstores Walgreens Boots Alliance, CVS Health and Rite Aid and drug distributors Cardinal Health, AmerisourceBergen and McKesson.

Walmart, which sources said bid on PillPack for less than $1 billion, lost $3.04 billion in market capitalization on Thursday.