This is an interesting article about stars who are against photoshop or think it portrays an unrealistic expectation about how they look on magazine covers
This is just a fun YouTube video with examples of altered pictures. This shows all the aspects of Photoshop and the tools that can be used to deceive viewers. Many are obvious, but some make you double-take.
Here's a great story related to the issue Milan raised of authenticity in photographs -- during any disaster, lots of fake photos circulate, such as these "from" Superstorm Sandy.