Part of that last update was an effort in that direction. I'm definitely a fan of pull-based curation; however, we didn't find much evidence that people were looking to use it. Presentation is an issue too. insomniasexx has been working on a redesign, and in it she has a follow icon, which reveals a drop down list of things that can be followed. But, even then, things get pretty complex with such a schematic. Consider if I make a post linking to space.com, tagged #space and #mars:

  mk
  mk.space
  mk.mars
  mk.space.com
  #space
  #mars
  space.com

And that doesn't include a community tag.

There is also the issue that some people like to use personal tags for specific content. That is, I might want to use the tag #music.mk specifically for music that I want other people to hear, but not for articles that relate to music or the music industry. Of course, I could make #musicilike.mk. But, I think personal tags are more likely to be followed when they aren't created for every post, as they then suggest that the author is doing something with special intent.