Pretty much every smartphone that I've owned, I've dropped at least once. Usually from hip-height to the carpet, concrete, tile or asphalt. I've never actually broken one - although one time I dropped an iPhone 3GS from about 2 meters onto tile (I had balanced it on the edge of a shower partition to listen to music and it fell when I opened the shower door), and I bent the headphone jack a bit. Another time I left my iPhone 4S on the roof of my car when I drove to work (it slid across the roof and got stuck on the rear windshield wiper). Yeah, I'm clumsy and I'm stupid... I know.
But I always use a case. I am obsessive about keeping my phones scratch proof, and I know that I'm clumsy (and occassionally stupid) and so I put a screen protector on and I keep a good cheap plastic Amazon case on them at all times.
I remember once, I was late for a plane at Denver Airport, was running with my jacket slung over my shoulder, turned the corner and my original 1st gen iPhone - which I paid full price for - flew out of my jacket pocket on my shoulder, flew through the air... and time slowed down and I watched it gracefully fly at shoulder height through the middle of terminal B at DIA.. and then it landed on the marble tile floor and slid about 7 meters feet before stopping. I walked over and picked it up and there was no damage at all, although the case was a little scuffed.