Wouldn't iPhone 4 cases make the reception even worse??

[RonHC]

Especially the Bumper, my iPhone 4 only has 1 bar when it usually has 3-4 bars [on iPhone 3G]

EDIT: Its been "No Service for an half an hour

 

[admanimal]

Most (all?) cases are made from materials like plastic and rubber, which do not interfere with radio waves nor would they cause unwanted conductivity between the antennae.