An issue of Safety
This should probably go in the general area. But I though it might be appropriate for beginners.
Last weekend I saw several of the plastic spinners shatter and hit 3 guys in the eye. No one was injured. 2 of the guys I saw had glasses on, but they were not specifically safety glasses.
When working around spinning props, it's a good idea to have some sort of eye protection. These guys could have easily been injured if the glasses had not stopped flying parts.