...a number of the more popular services strip this embedded information from images when the images are uploaded to the services or processed on their servers.This created quite a discussion in one of my classes last week! We recognize that this stripping of metadata is affecting all of us, but we know that it is affecting professional photographers even more. Embedding metadata in a photo is done by the camera and editing software. Metadata - including information on who took the photo - can be quite helpful when searching across photos or even demonstrating ownership. Strip that information out of the photo and that photo could have been taken by anyone at any time.
Why would a social media site remove the metadata? My guess is it is part of the file resizing that occurs, since sites like Facebook really don't want to be storing large files. They would prefer to resize the files to something more manageable. That does mean that the file you have on Facebook is really not the same as the photo that you took.
The report does include information on social media sites that do not strip out the metadata. I'm saddened to see that Flickr, which is use heavily, didn't do well in the tests.