[Muncle]

Boy I hate it when people do this, but

I suspect your moderately conservative estimate of 30K carts is fairly close to accurate. And I agree that, like cars, if they really want your cart they're going to get it regardless of any theft prevention short of Couzin Bubba (not Bubbalarry) with a 12 gauge sitting in the front seat. As you say, just use common sense and, if it happens, it happens.