Sunday I dashed into the supermarket to pick up a couple of things and was meandering my way to the checkout when I happened upon five kids (one girl and four boys, age range roughly five to eight) riding skateboards (from the store shelves) up and down one of the isles.  No adults were around, so being the next best thing, I felt some weird wave of societal duty wash over me and force me into action.

The dialogue went something like this:

Me:  Hey guys, it's probably not a great idea to be riding those things in here. Are your parents around anywhere?

(Much shaking of head and general gesticulation in vague directions. Pause of awkward silence during which I start to realise that I sound like a grownup.) 

Me: I'm not trying to be a jerk or anything, but if you fell and whacked your head on this floor, you'd be seriously hurt. Not to mention that you could wham into someone else and hurt them, too. Notice the helmets on the shelf there, right above the boards?

(Kids all nod silently.)

They sell those things so that when you fall, you won't get hurt.

Random Kid: Yeah! My dad always makes me wear one when I ride my bike.

Me: Right! Exactly! They're kinda important when you're on wheels of any sort.

(Looks from other four kids tell me that my effectiveness is only at 20% thus far.)

Me: Look, have you ever dropped a watermelon?

(Three vigorous nods, one look of confusion and one shaking of head.) 

Me: This floor here is harder than concrete. It's harder than your driveway. If you fell hard on this floor, your head would smash like a watermelon.

(Ten eyes wide with horror.) 

Me: So you probably shouldn't ride skateboards in stores, right? And definitely not without a helmet?

(Much nodding all round.) 

As I was leaving the store, it occurred to me…… did they head directly over to the produce department to test my information?

Oh well, as John said when I told him, "Not my watermelon, not my driveway."