Apple says other smartphones, such as the BlackBerry Bold and Droid Eris, have the same problem with signal attenuation when the devices are held.
Mobile phone signal attenuation happens whenever a signal is obstructed, Apple notes. The density and composition of the human hand can cause attenuation to a greater degree than some other materials.
On a mobile phone, signal loss typically occurs when your hand attenuates the most sensitive part of the antenna. Apple even has put together videos demonstrating how different grips cause attenuation on many popular smartphones, not just the iPhone 4 and iPhone 3GS.
