I still seem to have problems with this. I have two colleagues who have access to a notebook I've shared with them. They don't just see the tags that have been used in that notebook, they see all of my tags including ones they really shouldn't. Based on the descriptions here that say that isn't how it works, I think a glitch has happened here. I tested out Scott's May 2014 post about selecting a notebook and then clicking on the 'Tag' icon to just see what's associated with that workbook. Again, mine hasn't worked that way. There's reams of tags with 0 associated items (because they're pegged to my personal workbook).