I'd rather the phone be plastic and have a removable battery than be brittle and break if you drop it on a hard surface. Sturdy build materials are nice but not if it means a guaranteed shattered phone if you drop it like the iPhone. Phones aren't jewelry; their most important feature is not how pretty they look or feel. Phones need to survive everyday use. I prefer using my phones naked but a case of course negates the aforementioned.
This.
My Samsung Galaxy S II has dropped at least 4 times well more than 3 feet.
There's not a shred of cracked glass anywhere on it, unlike there would have been if it was a HTC or Motorola phone.
When my phone falls, the only thing I know that always happens is that the plastic back cover flies off.
What's the science behind that?
I'm guessing because it does that, energy is directed upwards into the air instead of back to the phone itself. If it had a metal cover, the energy would be directed back to the phone which can easily cause the glass to crack?
I'm not a physicist, engineer or scientist. I'm merely drawing conclusions based on my own personal observations and also some "drop test" videos.
Whatever Samsung did with the Galaxy S II, they did it right. It has excellent durability.