I'm going to disagree with this as well. Sure the S3 feels cheap because it feels so light. But the fact is that the polycarbonate materials used for the body are actually quite forgiving in a drop, and will hold up far better than you think it will just from holding it in the store. As far as the screen goes in a drop, the Gorilla Glass 2 should fair better than standard Gorilla Glass. And as huskar said, this type of body can help in possibly preventing some damage to the screen by flexing a bit. A metal or harder plastic like Motorola uses won't allow for the same type of flexibility and forgiveness. All of that said, husker was right in his first post - things happen. Any device, no matter how strong it is, has the chance of being broken in a fall depending on how it falls and where it falls. One person could drop a device 100 times without any major damage, and then another person could drop the exact same device once and essentially total it.
Personally, I prefer the build quality of Motorola devices, and I think Samsung has a lot of room for improvement. That said, your snap judgement based on a brief time with the device in the store doesn't take everything into account. Samsung wouldn't put out a major device like this if it was going to "demolish" every time it gets dropped. It feels much cheaper than it actually is.