I had two ideas which are accomplish the same goal - let you share your pictures online without giving them a chance to realistically reuse it for other purposes.
Facebook - Instead of a small watermark start using a large text based watermark that gets displayed several times across the image - ie. FOR FACEBOOK USE ONLY - COPYRIGHT YOUR NAME. If somehow in the future Facebook decides to use your image for whatever they want they will have a little reminder from you.
Photo Contests that want to own your pictures upon entry - By submitting a picture to the contest you are granting them rights to that picture. If you modify your original picture and insert a watermark that makes it a new picture. Let them own a picture that is low-res and with a large watermark. Good luck selling image like that.
What do you think guys?


