Hmm – see the full post for more details
On the surface, it seems like tags should be helpful, Budiu said, since they increase a user's engagement with an article. In addition to reading, the user considers what tags to give it and enters them. It sounds similar to highlighting key passages of a textbook, or making notes in the margin. So why should they reduce recall?
Budiu found that adding tags cut into the time that each user spent actually reading an article in the first place. In other words, paying attention to tags came at the cost of paying attention to the text.