I have already posted about what Google’s PR or PageRank is. Many of the SEO Kiddies live for the day when Google “update” the PR every 3-4 months (when in reality they update it every day internally). Many of the SEO Kiddies and the SEO experts have dismissed PR as no longer being important in the ranking of the site. While they are not being totally honest as many factors go into the ranking of the site in the SERPs and PR is just one of them, what they are probably saying that the visible PR that we see in the toolbar is probably not important.
The best way to think about it is that the number of pages that we crawl is roughly proportional to your PageRank. So if you have a lot of incoming links on your root page, we’ll definitely crawl that. Then your root page may link to other pages, and those will get PageRank and we’ll crawl those as well. As you get deeper and deeper in your site, however, PageRank tends to decline.
A previous post discussed how to get more of a forum indexed in Google, so you can be found for the long tail searches. This comment from Matt Cutts confirms that PR is important when it comes to the indexing fo a site and for our purposes, a forum has a lot of user generated content that we want indexed. I get a lot of links to the deeper pages using Linkvana, but there are other strategies.