From Morning Brew
The backstory: Last June, Apple announced a tweak to iOS that would bar apps from collecting ad-targeting info (a string of numbers called an "ad identifier" unless users gave them the go-ahead. The change could present major headaches for ad-based apps...like Facebook. 

Facebook launched a full-on resistance campaign, taking out newspaper ads, publishing blog posts, and setting up a website outlining its reasons for opposing the shift. Those reasons? Facebook argued 1) the feature would hamstring small businesses and 2) Apple uses iOS to favor its own products. 

On Facebook's earnings call Wednesday, Zuckerberg warned investors that Apple's maneuvering posed a risk to Facebook's bottom line. Then yesterday, Cook responded with the business equivalent of "where'd you get those clothes, the toilet store?"

"If a business is built on misleading users, on data exploitation...then it does not deserve our praise, it deserves reform," he said at an online conference.

Looking ahead...the iOS change is scheduled to roll out this spring.