According to a growing thread in the Apple Support Discussions forums, the Apple bumper case, made specifically for the iPhone 4 (and a major part of the "Antennagate" solution), is scratching the steel antenna band.
ASD user Dayvidpriddy reports:
"I received my black bumper about a week ago now. Took off the bumper tonight to clean my phone down and there are scratch marks on the steel band from the bumper (this is caused from the pieces of hard plastic on the underside of the bumper."
Many of the comments after the initial post point out … Read more