The thread mentioned above covered the same subject but died about a month ago.
I agree with other posters that Facebook needs to have a non-exclusive right or "license" to publish your uploaded photos. Just like on this forum we agree to the publication of our images by accepting the forum rules.
There is a distinct difference in the wording used by Facebook:
You own all of the content and information you post on Facebook, and you can control how it is shared through your privacy and application settings. In addition:
For content that is covered by intellectual property rights, like photos and videos (IP content), you specifically give us the following permission, subject to your privacy and application settings: you grant us a non-exclusive, transferable, sub-licensable, royalty-free, worldwide license to use any IP content that you post on or in connection with Facebook (IP License). This IP License ends when you delete your IP content or your account unless your content has been shared with others, and they have not deleted it.
and the wording in the POTN forum rules:
1. (The ownership legalese)
This forum is international discussion forum about photography, photos, gear and techniques.
By registering and making posts on the photography-on-the.net Digital Photography Forums, you agree to abide by the Forum Rules of Use, both stated and unstated.
By posting messages to the photography-on-the.net Digital Photography Forums you give forum owner and maintainers permission to permanently store all message content, present it for public viewing, backup it to any location and media, present it in other form, modify *, delete, or make any use whatsoever in the Forums.
I am just a simple retired lawyer and certainly no expert in copyright law but I think that Facebook got/is asking for far more than they need to just publish your content. My apologies for the bold and coloured sections in the quote. It is just to help others read the legalese.
As others mentioned: they may not "steal" your photos for external use but with the current wording in their "terms" they can.
Others may think differently. There is a lot of speculation from bush-lawyers and other people that cannot read properly . I would like to hear the opinion of a real expert in this field (without paying a fee )