Here it is! The official response from Motorola (on a Sunday, no less).
"The Motorola ATRIX does not have an FM radio. We currently do not have any notifications if there will be an update to add this feature on the phone. We are always gathering input from owners from calls, e-mails, the Web and other sources. We do apologize for the inconvenience this has caused you and want to assure you that Motorola does value your feedback. We open a record for all consumer contacts which are then routed to the proper department for any further research."
I think that if the Atrix users unite and flood Motorola's customer service with requests to activate the FM receiver, we will have a better chance of getting it.