I am pretty obsessive about this too. I keep my gear in the trunk, with smaller items in the center console. I have been in an accident and had the radio come out of the dashboard; I'm just glad the wire harness held. My wife is pretty bad about loose stuff, but she hauls so much kid equipment that I can't talk her out of it. There's really no place in a minivan to secure the stuff; I could strap it all down but it would be so much of a hassle to her that she'd leave it all undone.

Another thing to consider is securing pets in the car; not only can they get underfoot when you're trying to brake, but they can bounce around a lot too. We hadn't even thought about it until our training instructor told us about an accident she was in. She couldn't get her dog in the car for almost a year because he was so afraid it would happen again. $20 for a simple harness that will clip to the seatbelt can save a lot of problems...