It's just horrible when that happens. I don't think it would be very easy to dognap Maverick or Nanook since they are both wary of people but Mikey loves any kind of attention. I do worry about that. I know there was a dog that was dognapped in the area and the owners were quite frantic. They had posters everywhere. Poor thing. I don't think they ever found it but I'll ask around.
My friend who trains horses had four pb yearlings in a pen right behind her house. These were the babies of everyone's favourite mares. Seriously, it seemed like everyone decided to breed their best, show horse that year. And someone walked up onto their property, haltered the horses and walked them off. They took them to a trailer that was parked by the highway and when the yearlings wouldn't load they just turned them loose. Three of them were killed by a semi on the highway.
It was heartbreaking for everyone.
That made me look into things like tattooing and microchipping. And what I found is that mircochips aren't as useful as you think since not every shelter/animal control unit has the means to read the chips and even if they do it might not be the right brand as there are different brands and they only read their own chip. You may have a better chance of having your animal identified with a tattoo if someone bothers to look up the information.
As far as prevention I think you should report anything you see as suspicious and don't encourage your dogs to get into strangers cars....
It is a real fear though. It's one of the reasons I believe in helping people get their dogs back (good owners). What goes around comes around.