I've dropped mine off an atv at 25 mph with no case and it didn't even get a scratch, then again mine is a rugged type phone, waterproof, dust proof, the works.
I dropped my old iPhone 4 once on a sidewalk and it got /decimated/. I've dropped this phone on a sidewalk, hardwood floor twice, and a glass table, and it has a tiny mark.
If you don't put a case on an iPhone its going to break. But if you have a case and it doesn't even have to be a nice one as long as it covers the corners it will be perfectly fine. All the people I have seen with shattered phones were ones that hadn't put a case on it. So basically all I'm saying if you like you better put a case on it.
THANK YOU OTTERBOX!~