Great article about this on Techcrunch:
http://techcrunch.com/2013/07/19/in-...olicy-kind-of/
It looks like they finally updated the nsfw explanation page (earlier it was showing a message that it was being updated) :
http://www.tumblr.com/docs/en/nsfw
It looks like the old chart is gone. There is also no mention of the "adult" classification. Only "nsfw". This could be very good news for many people here.
Maybe Tumblr will allow all content to be indexed by external search engines again and some of the sneaky hiding of adult blogs will go away.