I applaud all who make their family trees on Ancestry public (boo to Ancestry for making people join to view those “public trees.”). Many people, myself included, spend a great deal of time and money obtaining the information we place on Ancestry for other genealogists to use and to make their searches easier.
When you find a matching relative in another users tree, Ancestry allows you to merge that information with your own. When you use the copy to my tree feature, a credit to the original up-loader is attached to that image/document in your tree and rightfully so. Giving a small bit of credit is the least we can do for the original submitter.
However, some less than scrupulous individuals have circumvented this credit by saving those images to their computers and then turning right around and uploading them as their own work. This steals the credit, not to mention the documents and photos from the person that is the rightful uploader.
The only way to protect your photos and documents is to embed some sort of watermark in them prior to uploading. I have created the watermark below to place in my documents and will use a simple embossed text watermark for photos.
If you upload documents and photos to Ancestry, you may want to design something to protect your investment.
That said, there have been times I have downloaded photos from another user and then uploaded them to my tree. I do this because the photo may be faded, discolored or damaged in another way and I repair it. Even so, I always make a comment on the photo, originally submitted by_____.