Based on this story, Apple acknowledges the antenna issues.
Apple has responded with a statement:
"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."
To mitigate this problem, it is best to get one of the cases for the phone. Not only with a case do you guard the phones from drops, but also the reception issue is solved.