I am really surprised that this thread has gotten to page 4 and I haven't seen anyone mention the safety issues involved in depending upon random pax to make sure an overhead bin door is securely closed. What if the pax who stood up to close it thinks it's closed and it isn't? Or what if said pax just gives up because he/she doesn't want their bag gate-checked? And then the plane takes off, banks, and something falls out on someone's head. Seems to me that depending on untrained, perhaps Kettle, pax is just -- you'll pardon the pun -- opening the door to a nasty lawsuit.

I would think that, especially as we are constantly lectured that an FA's primary responsibility is pax safety, this would absolutely be a mandatory FA task.