Tim Parkin has written an article about Orphan Works and the Enterprise and Regulatory Reform Act and how it could potentially affect photographers (article here) and I think that's what Clive's friend was maybe alluding to. Many social media sites strip out exif data when you upload to them - including Flickr (although only when the image is downloaded). The bottom line is, as I think was stated in Ian Grant's post about someone ripping articles, images and text off other people and using it as their own - if you want to protect your images from unfair use with no attribution or licensing fee paid to you as the creator - then don't post them on the internet.