As per recent interview with Matt Cutts, the debate over the passage of link value and page rank with 301 redirects has been made more clearer. As per Matt Cutts the 301 redirects do not fully pass the page rank and values. Even though he is not 100% sure about the answer, he didn’t ignore the possible loss of page rank value as a result of the 301 redirects. During the interview Matt Cutts also stated that he was not sure whether the crawling and indexing team has implemented any sort of such natural page rank decay. But later in a follow email he stated confirmed that the fact was true.
Here is an excerpt from the interview.
Eric Enge: Let’s say you move from one domain to another and you write yourself a nice little statement that basically instructs the search engine and, any user agent on how to remap from one domain to the other. In a scenario like this, is there some loss in PageRank that can take place simply because the user who originally implemented a link to the site didn’t link to it on the new domain?
Matt Cutts: That’s a good question, and I am not 100 percent sure about the answer. I can certainly see how there could be some loss of PageRank. I am not 100 percent sure whether the crawling and indexing team has implemented that sort of natural PageRank decay, so I will have to go and check on that specific case. (Note: in a follow on email, Matt confirmed that this is in fact the case. There is some loss of PR through a 301).
So going forward it would be better to keep this fact in mind.