Dear Mythbusters,
Growing up my parents all ways told me to never stick my hands out the windows of a moving vehicle. When asking why they would say because a boy about 14yrs old was riding in a truck with his dad hanging his right arm out the window. While trying to grab at some tall grass his arm got tangled in it and yanked off. Now I'm not sure if it is possible but could any damage come from grabbing at tall grass from a moving vehicle?

No. Not true.