As a former photojournalist, I can saw that you simply blacklist them and/or fire them from being a contributor/stringer/staffer at that image bureau. There are ethical standards in the professional photography world, and it is nothing bad to those of us who upheld our high ethical standards to see someone get fired for unethically altering images and cheating and breaking the rules. I doubt this is as much a problem from a "who altered their photos?" problem as it is the photographers are submitting larger files (even if lossy down converted into JPG from RAW) and Reuters is having problems handling so many large files in their infrastructure and pushing photos out in distribution to their newsroom client "on the wire" servers. I know in my past when dealing with AP, if you uploaded a file that was too large they either rejected it, or WORSE, applied their lossy compression using whatever software they saw fit. When what your image looks like is everything to a shooter, and when a perfect images is ruined by crap third party compression due to file size, the lesson is hard learned and PJ folks are pretty savvy getting the best bang per MB.