Doesn't work like that. Googlebot for example get and store everything. Then, somewhere during indexing or during the filtering for public access (most likely at the end, so that Google has it internally) the "nofollow" content is tagged
Google will never disclose the real objective/usability of "nofollow" tag. If google declared that it doesnt follow "nofollow" tag, then it doesnt necessarily means that you can add a-d-u-l-t or any other links on your website using nofollow 
. Webmasters around the world believe in what google openly said in any conference (BLAH BLAH BLAH), but they never come to know what Google instructed their search operators/programmers behind the closed doors of their lavish offices 
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Its best to rely on personal experience and online blogs. Several webmaters are still lurking in dark over the exact functionality of nofollow attribute, and how does it actually behave when confronted with Google, Yahoo or MSN crawlers. As per my experience, I feel that links with rel="nofollow" are kept in some hidden database and never shows up while searching back links for a particular website. However it could be possible that links with rel=nofollow have to undergo strict monitoring, but in the end they are treated as any other links. 
Hoping for the best. Meanwhile you can join read some cool articles on SEO at my online blog : http://groups.google.com/group/seohawk
Top Google Secret 1
Google told to its programmers "We are organizing a trip to Disney Land Tomorrow".
Google told its marketing team "We are organizing a trip to Bikini Island Tomorrow
Lesson1 : Never rely on Google Talks.