In the last few years there has been an explosion of Internet golf instruction. It started as a small movement mostly on forums, and now has grown to a point where individual instructors now have their own sites and forums dedicated to instruction. What has sparked this wildfire you say? Simple answer? The slow motion video camera.
When I was growing up, I was quite lucky to essentially live on a range. I worked at the course washing carts so I would get free range balls. Many of the pros who worked in the shop would come out and give me some lessons. During this period, the pro would watch your swing a few times, give you a few pointers and then be on his way.
I would go on hitting hundreds of balls and after a while I would go back to having many of the same problems. I could never understand why. Today I know, without a camera to track my improvement I would slip back into all the bad habits I developed and never really improve.