I always stop and ask if people are ok. And in my experience on the trails, I haven't ever even stopped to take a picture without someone making sure I'm ok.

I wonder if there's more of a sense of responsibility to ask on the trails, since it could be hours before someone else comes across the same stranded cyclist? I know I'd be more likely to ask a stranded motorist if they needed help (from the safety of my car) if they were in the middle of nowhere vs. the side of the interstate.