Apple has posted a terse Knowledge Base article acknowledging the whining noise some MacBook Pro users are experiencing. The article says, in full, "If your 15-inch MacBook Pro emits a high-pitched buzzing sound, please contact AppleCare for service."
MacBook Pro units that suffer from the problem emit a high-pitched whining noise from the keyboard area.
Apple offers several options for contacting AppleCare for support. You can check the Support Web page for the option that best suits you.[Thanks to Macworld UK for the heads up.]