This effect has been known for years.
That is what is so funny about this whole affair. There are videos on YouTube going back years showing various phones from Nokia to Motorola to Apple to HTC showing serious signal attenuation (and loss) when a phone is held a specific way. That really is a FACT all the Apple haters want to sweep under the rug so they can pretend this is new with the iPhone 4.
Can the iPhone 4 drop calls when held a specific way? Yes (I've Done it).
Can the Droid X drop calls when held a specific way? Yes (I've Done it).
Can the HTC HD2 drop calls when held a specific way? Yes (I've Done it).
Can the Droid Incredible drop calls when held a specific way? Yes (I've Done it).
Are these unnatural ways of holding the phone. In all cases, these are natural holding methods for some people. Some people grip a phone in the middle, some at the top and some at the bottom. Personally, I tend to hold these single all screen touch phones more from the top. So from that standpoint, it is EQUALLY easy on all the above phones once you figure out HOW to do it. One is not special. The iPhone 4 does NOT "detune" the antenna when the bridge is "shorted". The iPhone simply attenuates the signal when held at that point.
The final question is: Does this simple fact detract from any of the above phones in anyway? No.
Companies like Nokia, HTC and Motorola were idiots for trying to spin a web of lies by saying you could hold their phones ANYWAY you wanted without impact to the signal quality. Apple called them on their outright lies. Move on.
Antennagate is bigger than people think. I have been able to make a Droid X drop from a full 4 bars to signal loss by holding it wrong (just like before the iPhone 4.0.1 update). This makes me wonder if (for handset driven or carrier driven or both companies driven marketing reasons) the "bars" have been a lie for some time.