You got 90% right, but just one small word missing in this is the difference that is confusing you and everyone else. You said above that when Google gets a nofollow they take it as:
"I cannot vouch for this link. Please do not include it in your ranking calculations for the target site as it is not my personal vote for this website"
What it SHOULD read is this:
"I cannot vouch for this link. Please do not include it in your
PAGE ranking calculations for the target site as it is not my personal vote for this website"
This is only a message sent to Google on behalf of the SITE OWNER. Google does NOT ignore the voice of the end user.
The nofollow wasn't as much about eliminating spam links so much as it was eliminating the manipulation of the PR system. Since then though, they have used this to help separate the standards by which they rank information both in it's import and timeliness. Sadly, I don't expect they will be coming out with a 1-10 TrustRank bar this time around with the new recent updates to tell us how we are TrustRanking the same way we are Page Ranking
You are absolutely right about nofollow not contributing the PR. However, you are absolutely wrong that Google ignores these links and regards them as spam. All links are signals. Nofollow, as you have already stated comes from users, that means, its a SOCIAL SIGNAL. You don't think Google will pay attention to what users are linking about? Of course they do.
What is necessary though is having a variety of content, comment, social link elements pointing to your site from a variety of sources. What would be ideal in looking natural? Just take a look at what happens in the media or with celebs, and how stuff there rises to the top of Google at record speeds, then can drop off.
A hype story, becomes #1 for a few weeks for a particular popular social source, then disappears leaving behind only the news releases. The nofollows beat out the follows in these instances. However, if the source ALSO has the d0follow links along with the social links, they will remain #1 and almost unstoppable.
Think of your link campaign as the release of information:
1. Your new site/page goes up
2. Broadcast in social networks is made (usually by you, they expect that, it's what any decent business would do)
3. People pickup on it and start to link it themselves via the typical sources like social bookmarks, comments, blog posts etc. Nofollow links come flowing in. You get super excited because now you see yourself in the top 5 of google

4. Site owners pickup on your page now, and start to create posts/sites about it and create d0follow linking to your site within content. Parasite hosts, article dir, anywhere else you can get d0follows at this stage.
This is how something would naturally progress, so just build links in the same sequence when you launch your site.
Google would then see your site/page as the most relevant to that keyword as stated both by the people, and by webmasters (at least thats how it appears

)
Rinse and repeat 3 and 4 now ongoing and your site is just going to continue to dominate. D0follows indeed help you get anchored in the top SERPS, but you need the approval of the nofollow social masses also. Google DEFINITELY wants to see a healthy ratio of both.