This video has many good points about pull ups. Some of that I did not realize on my own.

YouTube - Pull Ups And Shoulders Injuries Rotator Cuff Injuries Due to Incorrect Form (http://www.youtube.com/watch?v=-ON2KLcWg6I)

When I was taught pullups, I was told to keep my scapula down to prevent myself from hanging from the shoulder socket and doing damage over the long term. I didn't find doing so made the movement particularly difficult or anything though (it was hard on its own :P). I wonder if I'm making this mistake?

I let my scapula rotate up, because the scapula has to be up for you to lock your arms out, and that is the standard. I've been doing pull ups like this for about the last three years, and I've never had an issue with my shoulders.

The video is interesting, but poorly done overall. The presenter does not really explain himself until over halfway through the video, and there are no actual examples of what he's talking about. It's not hard for me to conceptualize what he's talking about, but it's possible it could be for others.

I do chinups since I'm not strong enough for sets of pullups, and I pull my scapula down when at the bottom position but to be honest I forget all about that once I start pulling. I haven't had any mobility problems [I get my chest up to the bar] so I suspect this would only be a problem if you were deliberately focusing on pulling down your shoulder blades.