Doesn't Facebook strip metadata when you upload anyway?
The Enterprise and Regulatory Reform Act is a huge piece of legislation created to improve Britain’s business sector, and most of the points in the Act are as important to photographers as the Littering from Vehicles Bill or the draft law to ban wild animals in circuses from 2015. But two thirds down the list of measures the ERRA will put into effect, it states: “For the first time orphan works will be licensed for use; these are copyrighted works for which the owner of the copyright is unknown or can’t be found. There will also be a system for extended collective licensing of copyright works.”
So without watermarks or proper metadata your images could be scooped up from the web via social media networks, app sharing, Google images or websites and used by anyone for any gain if your images can’t be traced back to you.