Not sure whereabouts you're from, but in the UK AntennaGate wasn't particularly concerning and I know plenty of people that kept their iPhones case-free, myself included, without glass shattering issues. Unless they were really, really silly and dropped it onto concrete from high up.

This is complete conjecture. Plenty of people use their 4s 4Ss without bumpers or cases with no problem, including me. It has be a design flaw outside of the base materials involved.

That's anecdotal though. My wife broke her 4S twice. What does that say?

I don't think you necessarily need a case to benefit: I don't use a case but slipped on a marble floor once and dropped the phone straight onto the floor, causing it to bounce a few times. The rim of the glass dented (what looks to be a thin plastic coating on the side of the glass?) but nothing shattered.

In any case, IIRC, speculation is that only the screen side of the iPhone uses Gorilla glass, but I'm not sure if that's changed with recent generations. But even without Gorilla glass, you can still use "standard" toughened glass that, correctly mounted, should never shatter just from the sort of thermal shock described in the article.

I have a 4S that slipped from my pant pocket onto a rough concrete floor from sitting height. The rough surface dented the plastic trim, causing the glass to shatter. I believe they went with the plastic trim due to the problems of joining glass and metal. But the plastic trim is the iPhone 4's Achilles' heel.

If we want to get anecdotal I used my iPhone 4 from launch with no bumper (even after I got the free one). I even dropped the phone three feet directly on it's top left corner and only the dented the metal band.

Twice I've dropped my un-cased iPhone 4s from a height of around 1 meter onto a solid tiled floor, and to my surprise not even a scratch.

Maybe I just got lucky, but in my limited experience, the case is not needed to protect the glass.

Most phones will usually survive such a drop. It all depends on how it lands. Phones with a glass back have double the number of ways that they can break when they fall, but it's still less likely to break than not. Drop it enough times and it will eventually break.

But the OP is talking about breakage due to thermal shock, not to physical shock.

The glass on the iPhone is actually quite resilient. The problem is the drop on one of the 4 corners (technically 8). At least that is my theory. All of the broken glasses I've seen have started at one corner and radiate out.