Why is the final trade of a librarian always a nametag? I can't imagine what I'll do with all the ones I get from fishing and from various chests. I have over 2 stacks of them now and find more all over the place.
It would be a lot more useful to have at least a random choice of something that might be more useful. As an instance, my armorer had all four pieces of diamond gear as his last two tiers of trades, two as Expert, and two as master. Makes it easy to rebuild my gear if I lose it somehow as I have librarians selling every spell but Efficiency that I need.
Villager trades have been much less random since 1.8, unless it changed very recently - they will always offer trades from the same limited pool per tier; by contrast, they previously randomly chose a new trade each time you traded their final offer (or gave discounts on existing trades if they chose one again and it cost less; this included enchanted books so you'd want to buy everything you wanted when you got it. This also meant that it became harder to unlock new trades as they ran out of new ones - but you could have things like a single blacksmith selling every single diamond tool and armor, which took me about 6 months to get, albeit I only traded as necessary to buy items for repairing my gear or to refresh locked trades).
Interestingly, in this case the most common final offer (in theory) was gold for emeralds when they didn't already have it as a normal offer (all other villagers had a very low chance of choosing this as a "default" trade; I've traded the "final" offer (wheat for emeralds) of one villager hundreds if not thousands of times without getting it yet; just in case it does I have a second villager as a backup, so this really is more theoretical than reality. Otherwise, the final offer can be anything, with less common trades being more likely).
As for the general availability of name tags, dungeons are the only source in 1.6.4, yet I have an entire chest full of them in my first world, where I've estimated that I've found over 1,500 dungeons, perhaps 3/4 of them in 1.6 chunks. Note that they were made less common in dungeons in 1.9, while being added to many other structures, along with fishing in 1.7 and trading in 1.8, so you no longer even need to explore to find them, which IMO makes them less valuable; likewise, I consider moss stone to be valuable dungeon "loot" as it can't be crafted.