Ah, this is why Apple is offering iPhone 4 Bumpers. The main use is not to protect the iPhone 4 from damage, but to protect against dropped calls.
As reported earlier, reports appear that the iPhone 4 drops calls when holding it in your hand.
Engadget confirms this and is more specifically pinning it down. Only when bridging the gap in the frame, which doubles as antenna, with the palm of a hand the signal fades.
Using an iPhone 4 bumper the issue is not occurring. To make things even weirder, Engadget says their review unit is not suffering from this issue.
This sounds like that some iPhone 4 from the first production run are faulty. As there are no replacement units available right now, you can temporarily fix this with a Bumper selling for $29 on the Apple Store.
Apple says that Bumper is really the Solution to the Reception Problem in iPhone 4.
More iPhone 4 News.
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