A few days ago I downloaded a third party iOS library, written in Obj-C. It was provided as part of a paid cloud API service. After integrating it, I was amazed (horrified?) to find that the whole library had been implemented without class prefixes. There were multiple collisions with Swift classes in my project.

Surprisingly the app still compiled, but tried to use the library class definitions instead of my own. I didn't end up using the library, or continuing with the API service.