Even the Fedora project in the FC3 era understood that running their own infrastructure on Fedora was taking more resources than they could spend. That's when they moved to CentOS for their infrastructure instead.
Lots of Fedora developers also admit using CentOS for everything where they need stability or simply don't want to update every X months. There is no controversy anymore. It's the same codebase with a different deployment target (for the same audience).
Within companies you can also see companies mix CentOS and RHEL, depending on the support needs they have for different systems. Business or mission-critical solutions running on RHEL, and testing or development systems running on CentOS.