Facebook thinks Amazon's ad business has officially become a threat (FB, AMZN)

Facebook listed Amazon as a competitor for the first time in its annual report.
Facebook says it competes with Amazon in advertising.
Amazon joins Google, YouTube, Tencent, and Apple on Facebook's official list of rivals.Facebook has a new rival: Amazon. 
The two companies have occupied the tech industry's top ranks for years, and they have increasingly encroached on each other's turf. But on Thursday, Amazon's fast-growing online advertising officially became a threat in the eyes of Facebo