There is a massive online market in link sales as I have discussed in other articles. Many webmasters link building strategy comprises of obtaining links on pages with high PR with few out bound links (OBL). From experience I can tell you that there are better metrics to use for link building than Page Rank, although that is a topic that I may discuss at a later date. Sites with high PR can generate a small fortune from link sales alone. The trouble is where there is a high paying customer base there are always scammers ready to cash in.
Before buying any links ensure you check the site thoroughly! Below I have listed a few checks you should always carry out before obtaining any PR links.
Firstly using Google type the following:
After pressing enter, the information displayed should relate to the actual domain you are checking. If the data refers to another domain name, then the PR is fake, as it is being passed from another domain.
Next go to www.checkpagerank.net
Again type in your domain and press enter. Check the display results to ensure the PR is valid.
Even if the domain passes the above checks there is still no guarantee the PR is valid. The major flaw of the PR toolbar is that the data is only updated on average once every 3 months. Many scammers use a high quality PR domain redirect it to a domain without PR. They do this a few weeks before a scheduled PR toolbar update. As soon as the toolbar update has occurred, they then remove the 301. At first you can check for this using the methods listed above. As soon as the original site has been crawled and indexed again the above tools are useless, as the site with the forged domain appears to be valid, so we need to run further checks.
Our final check should be to use back link checkers to look at the amount and quality of back links the domain actually has. As a very basic guide the domain should have at least a handful of back links that have the same page rank and at least a couple of back links with PR higher than the actual domain. For example if a domain is advertised as PR4 and only has a few PR1 and PR2 back links, then it is safe to say the PR is not going to retain PR4 after the next PR toolbar update. For a PR4 domain I would expect to see good back links mainly PR1 to PR4 with maybe at least one PR5 and maybe even a PR6 back link. It is thought possible for a domain to have a valid PR4 with just one or two PR5 links.
I have even seen one of my own sites pick up PR4 with only one solid link from a PR4 site although this site only had 2 OBL.
A good analogy is to think as Page Rank as water in a bucket, with external links acting as a hole in the bucket. Of course the more holes in the bucket (external links) the more the water (page rank) will flow out of the bucket.