Damn, missed that. How do you check, rectify for that? aside from honesty? It's a matter of the more authoritative source, so how do you check one link is more authoritative than another algorithmically?
Moreover, tagging leaves open the option to build recommender systems through collaborative filtering. I believe one of the reasons Reddit's recommendation tab was broken for so long (and still is) was because it was difficult to relate content without the use of tags.