FWIW, I'm with Shiny and contentiouscat and I have sympathy for MrR's view.
You cannot shield the world from children. The news will seep through to them however much you try. They might see a poster or a newsreport on the TV. Or attend a movie and see the ad. Fact. And they will ask questions, which it is our job as parents to decode for them at a level they understand, coated with a large amount of reassurance.
Tbh, children are more frightened by parents' reaction to news, than with the actual news themselves. So whilst I don't give the news to them in technicolour with dire warnings of baddies lurking in every corner, if they ask, then just explain it in a simple, non-sensational way. I agree the word "snatched" is emotive, but then just downplay it and just say she was lost. But you will keep dc safe.
If you don't make a huge issue of the word or the ad, they won't. If they get scared, then reassure. My children are welcome to sleep with me anytime. What would terrify me as a child was having seen the ad, my parents then got upset and starting going on the warpath without explaining fully.
Children will gradually absorb the message that the world is unsafe. It is part of growing up. To the little ones, they just need to know that mummy and daddy will keep them safe. As they get older, they can be told the tools of keeping themselves safe. The message is just drip-fed to them over time as part of life's education.
The Madeleine abduction is not the only thing. A grandparent could die, a pet could get knocked down in a hit-and-run, sh_t happens. We just have to be there for our children when it does.
I don't see it as a big deal.
And Madeleine's parents are entitled to do everything in their power that they feel will bring her back (whether or not you agree with their tactics). I support them. Even this discussion is keeping her image in your minds. I don't think they would be unhappy about it. I cannot imagine their pain.