I allways wonder when I read storys like this, do they realise leylandii normally grows to 70+ foot (to give you a comparison, my massive three floor vicotrian town house is towered over by a leyandii), and about 50 feet or more in width. You are talking about planting a tree that can grow to about the size of a tennis court in rows with probably only 2 or 3 foot between them!

Once, in a never to be made again mistake I planted a leylandii hedge. It grew fast out of control and the roots made the soil in a massive area below them dry and acidic, so nothing grew well there. They are also a major fire hazard according to the local fire department, they're a very dense waxy plant that will easily catch fire without anything like petrol as a starter, just a burning newspaper shoved in one starts a massive fire that's very hard to extinguish! It's worrying to realise just how many people have planted such a flamable plant in massive ammounts in small gardens, I've seen many which have so many leylandii close together that if one caught fire the whole garden would go up, and they plant them next to buildings and wooden fences, even lining driveways with cars. More worryingly yet, because they're so thirsty during the hot months there's no lack of dry dead leaves and grass below them...

I don't dislike leylandii, but I think people could be a lot more careful with how they plant it. A better hedge would be something like yew or holly, neither are vigirous plants that need constant trimming, and some plants have thorns and dense growth that wards of vandals to some extent. You may also find in a less formal garden it's more attractive to have a varity of plants in the hedge.