one of the local admins in red deer did a test with mechgoggles, often the bbs would shatter sending small particales into the users face. i think theres a youtube video of it somewhere. as well, if a hot gun is used, over a small period of time the mesh will weaken and eventually break, not good if you ask me. i use 5.11 tactical glasses and usually don't have a problem unless its super hot out or im laying in deep grass.
"Those who have long enjoyed such privileges as we enjoy, forget in time that men have died to win them"
Franklin D. Roosevelt