You know, I really don't know about the permission level for adding/reading the properties. As I mentioned in my post, it is still just an idea I'm toying with. I suppose if security was an issue, it could be addressed by a role allowing users the rights they need for extended properties, and then adding those users or groups to the role.

We have so many other issues to tackle it just hasn't been high priority and there is also a push to get some sort of third-party tool in here for capturing meta data. I believe many of the third-party tools use extended properties as well, so I've been holding off to see where that goes.