Upload & Sell: Off
Everyone does realize that whatever you post to FB with "Public" privacy settings is, according to FB's Legal Terms, granting FB a non-exclusive license to use the image for free however they like, including sub-license it and sell it forever or for as long as the image is anywhere on FB. Even if you delete the image or your FB account, if a client posts your image to their FB pages, and those aren't "Private", then the image is still licensed to FB. Do your clients know this and is that ok with them? (I'm assuming FB would need a model release for any pics showing a face; and a property release for a recognizable structure; but all else is fair game.) FB could be the biggest microstock agency if they decide to exercise their rights (if they haven't already).
Go try to find where to change your privacy settings, I dare you. Most folks won't be able to find them easily or at all.
Read the legal terms, especially section 2: http://www.facebook.com/legal/terms
(if you didn't find the page to change your privacy settings, you can click on the link in the legal terms.)