My inbox has attracted quite a lot of emails about this so I think a post is in order.
Yesterday Verizon announced its very own iPhone 4. Externally, it's almost identical to the AT&T iPhone 4 ... except it's not 100% identical.
In order to make the handset work on Verizon's CDMA network, Apple had to redesign the antenna. The antenna redesign has meant that the mute switch and the volume buttons on the side of the phone have been moved down a few millimeters. Just a few millimeters, but just enough to ensure that existing bumpers, cases and skins won't fit the Verizon iPhone.
OK, you might get lucky and manage to stretch the rubber a little to make it fit, or perform an operation on your existing case to make the mute switch hole a little bigger, or you might just live with having the mute switch covered. Or maybe you'll just leave your iPhone 4 nekkid. Whatever you choose to do, don't be caught out by this small design change.