What's wrong with this technique?

Olejka

Hi, I'm a huge fan of Glenn Danzig And I'm really influenced by his song writing and his vocal abilities, Though I think every Danzig fan out there has noticed that he lost his power and range overtime, and I wanna know what was and is wrong with his tecnique? Aslo I've read on the internet that he actually has never taken a single vocal lesson and I wonder how he was able to sing that strong and powerful for a pretty long period of time? 
http://www.youtube.com/watch?v=vgSn0SbQJQI gonna leave this song as an example
P.S I'm russian so I apologize for my english skills :P

highmtn

He is oversinging in order to get the type of distortion he is using.

This is unhealthy and will wear your vocal cords out.  Essentially he is shouting with no regulation on the air.  This will destroy your vocal range.

Don't do this to your voice.

 

Bob