Apple has finally acknowledged that the way you hold the iPhone 4 can hinder the device's cellular reception.
when the iPhone 4 is gripped in a particular way--usually by touching two seams of the antenna band on the exterior of the phone simultaneously--began popping up late Wednesday night, and continued to appear Thursday.
While Internet commenters and bloggers spent most of the day trying to figure out if the problem was related to the phone's hardware or software, Apple released a statement late in the day to PC Magazine.
"Gripping any 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 Phone 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."
There are two antennas on the iPhone, which are built into the steel band on the exterior of the phone. The one running on the left side of the phone is for Bluetooth and Wi-Fi, the one on the right is for cellular reception. That means how a left-handed person holds the phone will affect it differently than how most right-handed people would hold it.
Steve Jobs said at WWDC the exterior antenna was supposed to help reception--he didn't mention there was a particular way you had to avoid touching it. However, if you don't feel like spending more for a case for the phone, it sounds like that's the cheapest solution.