If you seem to be experiencing an echo with your iPhone Defender case (most likely with 3.0 software or 3GS hardware) you can do the following:
There are two small white vents at the bottom of the Defender case, one on each side of where the charging port is. First, remove your phone from the case. Second, remove the vents and foam (if gray foam pieces are present) and it will eliminate the echo. When operating in speaker phone mode, we observed a small echo when using the iPhone with or without a case.
