Remember that Radio Shack sale that offered the iPhone 4 for $149 and caused a nationwide shortage in the Shack's retail stores? Well, Sam's Club is about to one-up Radio Shack with a Member-only promotion that drops the price of the iPhone 4 to $147 with a two-year customer agreement. The leaked internal communication suggests the promotion is available now and extends until Christmas day. If you missed the Radio Shack sale, then should definitely jump on the Sams' Club promotion as this is likely to be the