This happened to me not too long ago. After I had done exhaustive research on my great-great grandfather, complete with several sources that agreed on who his father was, someone came along and changed his parentage and that of his two brothers to someone else. The only "evidence" for the change was found in three Findagrave profiles (which are not recognized as valid sources). I wrote to the person and asked if he had any sources other than Findagrave, and his only reply was to quote my message back to me. I put the profiles back the way they were and put an announcement in the "Notes" section of all of their profiles, as well as their mother's, stating that there is some confusion about the mother's marriages and the sons' parentage, attributable to (unsourced) Findagrave memorials. I referred the reader to the notes in the mother's profile which outline the extensive research and sources, ending with the request that if anyone has CREDIBLE evidence to the contrary, please contact the profile manager.
The real kicker was that the person who made the changes did not appear to be an inexperienced genealogist. I could only guess that perhaps he was not aware that Findagrave is not considered to be a credible source.
