If you put your hand over any cellphone antenna there will be signal attenuation. It is not limited to iPhone 4.
In the following video the Nokia E71 was tested:
It’s ironic especially after Nokia made fun on how to hold a phone.
The next video shows the HTC Droid Incredible, an Android phone on the Verizon network in the US:
Via Edible Apple.
Arabic version of this post on SaudiMac Arabic Edition.