I am new to DT and am pleasantly surprised to see that DT has in place a system for unauthorized usage. This begs the question of how and when to promote your own stock photography on other venues - particularly FaceBook, Twitter and other social networking.
If you own a blog you can promote your link to your stock photography portfolio in many different ways. So too with social networking - and this is perhaps the 'safest' way to do so.
The biggest challenge with FB and other social networking sites is that when users comment, upload or post anything onto the site, the user must be aware of the small print on the site's policy page.
Once uploaded...FB can own almost all usage rights to the photo, post or comment and can use them without buying the photo usage rights. They can use the photo in any way they please. The best course of action, should the artist decide to upload art, photos or written content onto social networking sites is to ensure that the copyright information is stated right on the photo by watermarking.
Even so, it is good practice to assume that the photo, artwork and/or written works WILL be 'borrowed' by FB and other users on FB.
Armed with this information we can then proceed and plan accordingly and will not be blindsided with any 'borrowing' that takes place. Because in the world of social networking, 'borrowing' is not only condoned but is encouraged. Make this work FOR you rather than being faced with frustration at unauthorized useage.