My kids both had chicken pox when they were in kindergarten and preschool (one caught it from the other one). At that time the vaccine was quite new on the market and not really an option for us. I do have friends that had their kids vaccinated and their kids got it anyway.
I honestly don't know if I would have had my kids vaccinated anyway. It's something that has to be repeated every 10 years or so, and my biggest fear was that even though I would remember to have them done once they got older they would probably forget. It's so much harder on an adult getting chicken pox than it is kids, and the chances of complications are much higher. I'm sure there are pros and cons to either situation. Luckily the decision was made easily for me.
I do agree that it's very selfish to risk exposing several people to it unnecessarily and hope they made a responsible decision.