Her [Lucas’ wife] first idea was to have
Threepio get shot, and I said impossible because I wanted to start
and end the film with the robots, I wanted the film to really be
about the robots and have the theme be framework for the rest of
the movie.
Talk continues in the comments over on the Star Wars Episode 7,8,9 topic making it the most discussed post on this blog. For those who want to go back to the source, I offer this 1977 interview with George Lucas from Rolling Stone Magazine.