aristotle - 4:47 pm on Jul 3, 2011 (gmt 0)
Google uses a logarithmic scale for pagerank. It's similar to the scale used for denoting the power of an earthquake, where for example, a Rickter 7 is ten times as powerful as a Rickter 6. So a PR8 is very difficult to reach, especially for a small site. If you have done so, that's quite an accomplishment.