I sent an e-mail to the Nature Valley folks (at General Mills) and asked them. I'll let you know what they say.
In the meantime, take a look at this marvelous passage from their home page:
"Our policy on suggestions and idea submissions
All comments, suggestions, ideas, notes, drawings, concepts, recipes or other information disclosed or offered to General Mills by this site or in response to solicitations in this site shall be deemed and shall remain the property of General Mills. You understand and acknowledge that General Mills has both internal resources and other external resources which may have developed or may in the future develop ideas identical to or similar to the suggestion or comments to suggestions and that General Mills is only willing to consider the suggestion on these terms. That, in any event, any suggestion is not submitted in confidence and General Mills assumes no obligation express or applied by considering it. Without limitation, General Mills shall exclusively own all now known or hereafter existing rights to the suggestions of every kind and nature throughout the Universe and shall be entitled to unrestricted use of the comments for any purpose whatsoever, commercial or otherwise without compensation to the provider of the suggestions."
In plain English: Don't give us a great idea -- because we'll just rip it off.