Back about three years ago, we covered an interview between Google's Matt Cutts and Eric Enge of Stone Temple Consulting where we thought we learned that 301 Redirects Do Not Pass Full PageRank & Link Value.
The truth is, they do not pass full PageRank but nor does normal links, which we knew. The issue was, most people felt that 301 redirects pass LESS PageRank than normal links and that is not true.
Google's Matt Cutts posted a video yesterday saying:
The amount of PageRank that dissipates through a 301 is currently identical to the amount of PageRank that dissipates through a link.
So currently, there is no difference between a 301 and a link in terms of PageRank dilution.
That being said, if you have many redirects, like chains of them from one url to another to another, that is a known bad thing. But one or so won't hurt you.
Here is Matt's video:
This is one of those topics that is pretty cut and dry but as you ask more questions, with more variables in the mix, it can become a "what if" type of scenario that is not so cut and dry. Which is why we had the confusion in the first place, because Matt did not want to lead people on the first time - I guess?