A media-literacy tool for the digital age

In the past week, two of my friends have called my attention to the PhotoShop Disasters blog.

We've all seen them: pictures that are funny, or just plain peculiar, and obviously--or sometimes not so obviously--improbable. Is it real life, or is it PhotoShop? Sometimes the illusion is so well done that it's difficult to tell.

Sometimes the results are funny. Sometimes, well, not so much.

Doctoring photos is nothing new; we can point to plenty of examples similar to the above in media from around the world, the U.S. included. PhotoShop, though, makes photo doctoring easier to do--though if the person doing the work isn't particularly accomplished at it, it can also be easier to spot.

When does such modification improve or clarify, and when does it deceive?