We have to see all the sides not only Backlinks. Have to submit in DO follow sites which will increase page rank little faster than normal.....
PageRank algorithm depends upon the back links (dofollow) in one or the other way. No other significant method to increase it beside backlinks.
I obtainted PR2 for 1 of my site within 2 weeks. I only made (more than 4)some qualiity and relevant PR3 backlinks.
I went on line on June 15 with my new website, A week later I introduced a Widget from Amazon in the Home Page and three days later I have got PR 3. Not that bad PR3 in 10 days!... But who care about that if my site was getting just 20 visitors per day! I think the PR is something like prestige... but it does not bring anything else, no traffic, no clicks, no money and I think that´s all about a Webmaster should be more interested. But if you like that thing about PR, just sign as affiliate in Amazon, put a widget in your site and wait...