One should not disregard the importance of learning music theory. Why? Because music theory is one of the essential tools needed to be learned in order to fully understand how music works. I know it's quite boring if you don't know its importance. But take it this way... Learning music theory is like learning the A,B,C's and the 1,2,3's of music. When I first opened a music theory book, I thought I was going to learn how to write music and how to harmonize a melody. Well, it's partly true since you'll be dealing with a lot of music lingo.
Music theory is just an introduction to a very broad world of music. It doesn't teach you how to harmonize a melody or what chord goes best after another chord etc... etc... But it does teach you how chords are formed and where do scales come from and a few dozen other things. You might be asking if you really needed to learn music theory to be a rock star.. My answer is Yes and No..
YES because before you can learn the subjects Music Harmony (art of harmonizing a melody using chords) and Counterpoint (art of interweaving melodies), you need to have a solid foundation in music theory.
And NO because some rock stars are just full of crap. So it really depends on what direction you are willing to take. If you are thinking about writing some good music of your own some day, then you should start learning some music theory. But if you are just one of those who would like to play some of the latest licks without actually asking how did the artist came up with that, you don't really need music theory. You just needed a guitar tab downloaded from the internet and go on with your thing.
I know a very helpful site for those who wanted to learn music theory. Go to http://www.teoria.com/tutorials/index.htm. Each topic here is presented in flash animations with sounds. It also has some exercises so that in a few days or few weeks time, you'll have a solid foundation in music theory depending on how much time you put into it.