Is it possible for a site to have non-fake pr if it has pr6 and have zero google backlink? Also if a site have no incoming links(only from that domain but not external links ) is fake pr for sure. How those guys can have pr6 how they do it.Buy high pr link at time pr updates or something better?
PR could be faked, thats why there are valid PR checking tools. but just because the site doesn't show any backlinks doesn't mean that site doesn't have any. google doesn;t show all the backlinks and often takes long to update thebacklinks. the site in question can have fake PR but at the same time might have valid PR and the links are just not showing. use a vald PR checker tool (just google it) to make sure the PR is not faked
Before everyone was aware of it, people could sell them for $$$. I.E. Get an old domain, forward it to a high PR site, get the PR, and sell it on any no-one will notice until the next update.
This maybe the case of dropped domain. I believe these domains will lose the PR on the next update even if the PR checkers are showing valid PR at the moment.
I believe if you have LOTS of "internal" pages pointing to your homepage you can get PR1 but getting PR 6 without any backlinks from external sites has to be a fake PR using redirection from expired domain.