said 6 months, 4 weeks ago:
I think this should be considered as a promotion and it should always have its place somewhere else than in news feed – with regular rules. For example on the tab within your page. (Section E here: http://www.facebook.com/page_guidelines.php).
You also need participants emails, because you can not notify winners through Facebook functionality like posts, messages, etc. Or do you use some 3rd party app for the Fan of the week selection, where the emails are being collected?
Let me know if you need more information!