My guess is..... Google devalues blog backlinks, since anyone can post one...... to be honest I think theyre almost next to worthless.......... a blog spam link can be equal to a real hard solid backlink on a site.... although iI would love if it was worth the same, id just go put 1,000 of links on blogs
it's count as PR0 but you will get benefit from high PR mainpage, because there will be more bots crawling more often into your websites.