Definitely...Getty/AFP and Reuters (I can't comment for any other agencies) have very strict guidelines about what constitutes "acceptable practice" and cloning the guy out is NOT one of them.
I can only Crop, Alter colour/contrast or brightness. That's pretty much it...I think you can "flip" the image, but with all the logo's and sponsor info, there's not much point as it'll all end up backwards.
However, newspapers can do what they like (within reason). I cropped one of mine a little too close for what the paper wanted use it for, so they cloned another inch onto the picture and printed it...it was only crowd background, but I suspect that's as far as a publication would go.
I know that the Football DataCo have strict guidelines on whats acceptable as well...for example, you can't clone a different team shirt onto a player in anticipation of him signing for another team.