I happened to stumble on this amazing little plugin for chrome called Show Facebook Computer Vision Tags allows you to view in-depth data that Facebook generates about uploaded photos. Highly accurate.
How hard would it be to get this data from photos on facebook and implement this into lightroom tags or at least write it into the meta data on download?
I would pay if someone could write a plugin or extension that could do this in batch and offer photos as download.
Is there a plugin already in existence that can identify and apply tags to albums in lightroom?
If you're interested in automatic tagging in general, there are a number of plugins that provide it, using Google's technology or their own technology: Lightroom: Automatic image tagging | Photoshop Family Customer Community
But if you're interested in Facebook tags in particular, then based on the existing of that Chrome extension, I would think it would definitely be plausible to write a similar Chrome extension that downloads a batch of photos along with their tags.
You might repost in the Lightroom SDK forum, where developers of LR plugins hang out.