Apple has said there is a problem. They have never said there was no problem. In fact Jobs said "And so the iPhone antenna went through all of this. We tested it. We knew that if you gripped it in a certain way, the bars are going to go down a little bit, just like every smartphone. We didn’t think it’d be a big problem, because every smartphone has this issue...A lot of people have told us, the bumper solves the signal strength problem"
So why give away the bumper? Bc customers have said it takes care of the problem. A design issue that all cell phone manufactures have. Instead of covering up the issue by hiding it 10 pages deep into a user manual like Nokia and Sony do, they said its there, demonstrated it through the use of video, told the media about it in a press conference and then said if you experience this problem, get a case on us.
The problem, or design flaw as IOWA likes to call it, is a design issue for EVERY SINGLE CELL PHONE MAKER. Just look at the multitude of videos on Youtube demonstrating this ssue. Its not unique to Apple or the iPhone 4. The issue is that all cell phone antenna's attenuate when you touch them with your skin. Every single one of them does. Sometimes that attenuation can affect your call, especially if you are in an area of a weak signal. In the case of AT&T, especially in SF, there's a lot of weak signal areas. And in the case of the iPhone 4 the place you touch it to cause the attenuation is more obvious than other phones.
All of the iPhone 4s have this design tradeoff. The tradeoff is that due to the external attenna, reception is much improved over the 3GS. See below:
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New iPhone 4 - the verdict is in | The Daily Telegraph
So in order to give most people better reception in most situations Apple decided to use a design that would also have more attenuation. However, for the vast majority of people, they will experience better reception and call quality over all. If you don't want to believe that fine. But the numbers in satisfaction surveys bear this out and the sheer volume of iPhone 4 orders, even after the issue was widely reported also bear this out.