I realize that this is an older thread, but I think it's a very important topic, so allow me to add my two cents.
In short: I couldn't agree more with what the other folks stated here. Nothing comes close to face-to-face guitar lessons from a qualified teacher. A good teacher will be able to tailor the delivery of the content specific to the student. That is important, because all students are different. I'm not saying that a teacher will design individual programs for each of his students, but while following a basic outline, he will be in the position to tweak things here and there and adjust the learning pace.
And being a guitar teacher, I know that scrutiny over the student's progress is obviously also an important factor. When you have to meet with your teacher on a regular basis, you are more likely to keep up with your practice. That's just how it is.
I wrote a rather lengthy post on my website about this topic a while back ago, outlining what in my opinion the advantages and disadvantages are that come along with the different learning methods (online courses, face-to-face, guitar classes, etc.). Please note: the link below will take you to the post of my website, and toward the end of the article I am promoting my Beginners Guitar Course (Online course with full access to a teacher). Because I feel the article is objective and fair, I feel comfortable sharing the link with you. However, if you are someone looking for a teacher, I want you to aware of the fact that there are many other great guitar teachers here in the forum - and also, the lessons provided here at Guitar Noise are of top quality and come highly recommended.
Link to my article: http://guitaringenuity.com/learn-to-play-guitar-online.html