First let me clarify, why I count link juice and page rank seperately, because page rank is just a measure used by google for various purposes which we all know.
Back links (or link juice) is used by all services. Including all search engines, alexa and so on.
Ok so back to the point, there is common myth around bloggers specially that nofollow links don’t leak your link juice or provide back link. Sorry, but it does.
Is rel nofollow equal to dofollow?
No, its not, you can count it as of almost half value as dofollow.
Which means, if you have 3 links on a page, link A (do follow) and link B and link C nofollow, then your backlink juice will be divided in 4. Link A will get 2 parts of it and link b and link c will get 1 part of it each.
Now it seriously doesn’t mean you should start spamming on nofollow pages too! spamming is bad! really bad!