LOL I remember when TPM was coming out and we were talking about how the little kid (Anakin grows up to become Darth Vader) and our mate goes (without irony) "Oh, you've ruined it now..." thinking that we had spoiled the plot for him.Other people take the view that everybody knows who Vader is anyway, so why worry if we're shown that sooner.
It does sound funny, but a friend of mine watched all six Star Wars films starting with TPM down to Return of the Jedi. She had never heard of Luke Skywalker and Darth Vader and was genuinely shocked when Anakin screwed up the way he did.