There is a section of Google's webmaster tools that lists the external links they found to your site. In that list, I find every single del.icio.us bookmark anyone has to my site, as well as bunches of blogs with nofollow set, and so on. They may not carry a lot of weight - my own del. page doesn't get any trickledown from del.'s PR 8 home page either - but the links themselves clearly mean something to Google.
Interesting I just read up on an experiment that AXANDRA did when it came to the no follow rule and rankings. So like it says at the end of the article that:
While it is true Google does not throw the data away, that does not mean the link passes PR. However it may still give link text reletivity. That the data is not thrown away is seen by nofollow links showing in the "Google Web Tools" Links section. I have many links displayed there that are nofollow. From my experience it seems that the link text for these links does get applied to the linked to page. I do not beleive the PR does. But I haven't ran a test with a high enough PR nofollow link to be absolutly sure.
You really need to read the whole thread. This was already addressed here: http://forums.digitalpoint.com/showthread.php?p=3428365 -Michael
So, if I understand this right, Google DOES acknowledge the rel='nofollow' tag in a link. That's good to know, I will make more use of it now. Because you loose PR is you have too many outgoing links, right?