Does it do good or bad to your site? Will google know if the PR of backlinks fake or not? will google penalize both sides? Thanks!
If a page have a fake PR, it will not pass any PR juice, because the page don't have PR. The PR you see in the toolbar belong to another page. I don't know about Google penalties but I wouldn't take the risk because imho, there is nothing to gain
I think if you suspect a site of having fake anything, you want to stay well away from such site, not only will you not get the benefits of PR you may actually be penalised.