Well, I just don't like having to enlarge the pictures. They lose too much quality and become too pixelated. I'd rather have some high quality pics to work wth. I may not totaly give up on internet pictures though as I only have a few Elvis books.
Off course a scanned picture is better then a internet picture, but to me with internet pictures you must really use your creativity to the fullest. And with scanned pictures people tempt to get a little lazy and go for the easier designs.
95% of the covers I made are made with Internet picture, and I can go on for 2 to 3 years using internet pictures.