And of course, don't forget, film/print was also extensively manipulated in the darkroom. It was just a little more difficult and time consuming then.
I find it rather strange that manipulation was carried out in the darkroom without question, but now that it can be carried out by almost anyone with a PC, questions are raised.
If you shoot Jpg, maniplution is carried out by the camera's onboard processor. often by the photographer adjusting the "Parameters" or just using the default settings.
If you shoot raw you have manipulate the data. Otherwise you would have no image.
Even if you leave the raw convertor on the default settings manipulation is carried out by the software.
So as I see it all images are manipulated to a lesser or greater degree.
So I would say no one posts an un-manipulated photo.
Although I have noticed on another forum with a worldwide annual competition where no "excessive" manipulation is allowed, on one of the winning images the sky had been totally replaced.
http://community.dcmag.co.uk/forums/thread/202558.aspx