There was some pretty big pushback when it was first announced and i think they went into "let's fix this before trying again" mode.

Originally your contribution wasn't refunded, so if you "pledged" $5 a month and only visited a few sites, google kept the rest. They have fixed that, but i don't think they've made any "relaunch" posts or anything. Maybe they are planning something else before that?

Also it doesn't solve the issue of tracking scripts, so many people won't even consider it, and they are very vocal about it.

Oh, and it only works for google ads. So sites that don't use doubleclick or adsense aren't included.

Probably because it didn't work so well for Google.