Unfortunately that article doesn't cover all the bases (to be honest I'm not sure if any Doug Demuro article does). As someone else pointed out, not all states shelter that information from the general population. Take TX for example where everything is public record and a license plate number can lead to your driving record, criminal record, address, drivers license #, etc. Sure, there is nothing stopping someone in the car behind you from taking down your information at a stop light and performing the same lookup, but we're talking about a drastic reduction in risk by taking 10 seconds and blurring a number. Case in point... scroll through the TRD FJ Kit suspension thread and you'll find countless people who skimmed craigslist ads and FJ forums for other people's VIN #'s to give to dealers that required an FJ VIN to order. That was a fortunately benign act that was made possible by people posting their VIN #'s online (which is also available to anyone willing to walk up to the vehicle). People will always try and game a system, just because you or I can't think of a reason why someone would do something doesn't mean they won't.
As someone commented earlier, our vehicles are not luxury or exotic but to be fair, those aren't the vehicles that are being stolen either. Thieves will ALWAYS go for the lowest hanging fruit with the best return. Look at the Tahoes/Yukon's where someone can pop the window on the rear hatch and yank the 3rd row seat in less than a minute and sell it on craigslist for $500 all day long. A $1,500 gobi rack held on by a few screws? no problem. How many times do you see someone post that their ditch lights or light bar were stolen?
The point is, why take on the extra risk when it's such a simple act to blur an identifiable number?