Gripping any mobile phone will result in some attenuation of its antenna performance, with certain places being worse than others depending on the placement of the antennas. This is a fact of life for every wireless phone. If you ever experience this on your iPhone 4, avoid gripping it in the lower left corner in a way that covers both sides of the black strip in the metal band, or simply use one of many available cases.

Meanwhile we can also confirm that iOS 4 already hacked - PwnageTool 4.01 was Released. With PwnageTool 4.01 certain devices are not supported this is because they are not supported in iOS 4.0 or they are not supported by our software. But they're working on ways to get past these restrictions. Info here.