ok. ive been playing guitar for about 15 years. i was like you guys sayin that lessons werent necessary. until recently that is. my whole problem growing up playing guitar was that when i did take a lesson itd be with someone that could barely play and as a result i could often out play many of my teachers. So i never took lessons again. when i was about 21-22 i went to community college and started making contacts in the music world. I ran into a classical guitar instructor that had been playing for 30+ years and i decided to let him teach me. I had to pay a huge fee, but it was so worth it! he corrected many of my bad habits and turned me on to a whole new musical genre. Unfortunately, i was only able to learn from him for that semester
As a result, i can play beautifully now and any bad habits i used to have are now gone. I totally recommend taking lessons from someone like this and not some 18 year old punk-rocker wanna be who got a job in a guitar shop. otherwise, guitar lessons are indeed a waste of time and/or money.