My first DSLR was a D70, I bought used. I used it for 4 years before disposing of it. Recently, I uploaded a photo to my gallery and when I checked the EXIF data, if found a copyright by someone else. After removing the photo, I downloaded a reader for EXIF data. Every photo I took with this camera contains this copyright.
I know many of you already know this, but there are many who don't. Comments can be added in your camera. If you buy a used DSLR, remove any comments the previous owner included. My DSLR now includes my copyright statement.