There has always been hype about the Star Wars movies, probably going back to the re-release of the original movie in 1979. Action figures, models, McDonalds happy meals, Star Wars themed drink cups (collect the whole set!), video game tie-ins, etc.
As for spoilers, I don't remember much, even on the Internet.
I remember a news story from shortly before the release of Phantom Menace. Someone stole the film rolls that a theater had ready for the premier.
During the run of Return of the Jedi, there was a story going around that someone had walked into a theater early during a showing, shouted "Leia is Luke's Sister!!!!" and got chased away by a mob.