NotNull wrote:Difference metadata / tags (my opinion)
Metadata: properties of the document, like resolution, bitrate. Technical information
Tags: Personal information, keywords added

Couple months ago I came to the same conclusion and I wanted to open a new Thread about it. I wanted to write, but it did not happen.. So I'll take this opportunity here to write about it.
I will use your terminology: Metadata (properties, technical information) and Tags (Personal).
I think Microsoft leaded to a confusion when they decided to join together 2 different things.
They took Tags and insert it to Metadata/Properties. I think it's wrong. Mainly because when the user make personal tagging it is changing the binary code of the file.
What should be done, IMHO, is to leave Properties at their place, and move/take out the tags to be managed by database or other method.
Properties should be edited at the first days of the creation of the file, before its publication, and will include all the info the creator of the file wants to attached to it for whole file life. This info travel with the file from PC to another PC.
Tags will be used for Personal information, keywords added (Personal customization). This info shouldn't travel without permission.
What is the best method for Tags, whether it is hardlinks or another method, it needs more discussion.