The key to editing photos is the
clone tool. But just cloning stuff over the
unperson's face is not sufficient. You must hand edit the
pixels so that it is not obvious that it is cloned. Another good strategy is to clone, and then change the cloned areas to have about 5% transparency (95% opacity), and throw a rough
texture underneath. Above all, follow the principle that if you can see any of the original lines, they can too. If you're stuck for ideas of what to replace the
unperson with, try flipping the picture left-to-right. It will give you a whole new perspective on the scene. Don't forget to flip it back - there's nothing worse than a mole on the wrong cheek.
Actually, it's not always
evil to edit photos. For example, some of the photos I took of
Renn Fayre 2000 had, say, people's heads in the way of stuff. Removing the heads is time-consuming, but leads to much better pictures,
artistically. Just don't lie about it. That would be lame.