Absolutely Bananas has "5 reasons why EVERYONE should know how to Photoshop their head onto someone else's body." Reason number four:
4. Because you wouldn't want your children to know THE TRUTH about how you spent your younger years (knitting and sipping tea? Come ON!) With Photoshop, your history is yours for the making! Goodbye boring momma, hello fab new me!
Includes a link to a Photoshop tutorial. Link -via Look at This
That's the problem I guess, without sounding elitist, that people think it's easy to do and act like they're masters after one day of learning the program. Sure it's easy to grasp the basics, but you'll be spending considerable time if you want to make something that actually looks good and believable.