In my group rides, we're a fairly large group and experienced group so we just expect you to be paying attention. The only things we call out are large holes that are uncovered, cracked roads that can cause you to lose control, and train tracks. And obviously dangerous debris like glass, dead animals, large objects, etc. Last weekend, there was a big ditch in the road. Everyone called it out as normal, and then at the end of the paceline, someone went down. Turned out he wasn't paying attention, hit the ditch and turned his bars and flew over them. Always gotta look out for yourself regardless if people are calling things out or not.