Spaces vs. Tags

Currently: Everything is just considered a space. Spaces currently act as buckets to place your annotations in.

Idealy: It would be EXTREMELY helpful if...
Spaces - Work like a folder (just like they do now). With the added ability to have at minimum one sub-level and a way to drag to reorganize them in the dashboard.
Tags - Added to make it easier to filter annotations down within each space. Currently, I am doing this by adding hashtags to my annotations, but it would be nice if Memex's UI supported this natively so that the annotations appeared less cluttered and offered it as an added search filter option.