Ghost PageRank, or PageRank which is an estimated PageRank value based on a domain's current PageRank summation, has been the topic of conversation over at one of the HighRanking threads.
One of the forum members recently launched a site with tripod under a domain that looks to be in the format of username.tripod.com. In just a few days, his PageRank went to 5. Not bad. :)
The thread gets a bit off topic, but people do try to explain the concept of PageRank and Ghost PageRank at the thread named Can A 1 Page Website Have A Pr Of 5, How to increase my PR.