1. Эсли верить http://kenkai.com/google-pagerank-table.htm
PS: кому лень ходить вот цитата:
"We would say that since Update Jagger, it is worth considering a link from a web page of PageRank Two or above, as long as it is:
* On focus with your product or service
* The website's index page has a PR of 4 or above
* There are less than 50 links on the page
* There are no undesirable external links on the page
* There are no nofollow tags on the links
* There is no robots metatag on the page with the content," noindex, nofollow"
* The link is not redirected"