So have I, but none that were so drastic, that I couldn't recognize my own ancestors by family groups.
I'm not saying census takers didn't change records, I just don't have any reason to believe that they changed the records of any of my "known" ancestors, with a conspiracy in mind.
While the Walter Plecker case maybe true, nothing about the findings we have come across pertaining to our ancestors have given us the impression that somehow, aconspiracy was going on. Nor have we come across any evidence that he, or others like him, made their rounds to Harris County, GA.
I read a story that was written by a professional genealogy researcher who stated that one of their clients refused to pay the remainding portion of an outstanding invoice.
The client, who was white, refused to accept that quite a few of their ancestors were African and Native Americans. The article went on to say that the client had no problem paying the researcher as long as white relatives were being located and that the problem started with the discovery of the non-white ancestors.
Does this mean the client could be in denial? Or the professional, wrong, or inept? Or that every record searched by the professional was somehow fabricated? Or that census takers changed everything? Why then should any of us even bother to research our ancestral lines if most of what we're coming up is so different from what we were told?
Like you, I have no idea why some census takers may have changed records or what their motives would be for doing this. The only thing I can of right now is that some people maybe researching wrong ancestral lines. It happens all the time, especially with hobbyist and non-serious researchers.