Interesting, so their implementation has broadly expanded upon the original meaning of the attribute (and the one standardized as a microformat), and in recommending this be broadly used to fight against spam they've paved the way for an interesting time for everybody else?
Re:How rel=nofollow Works
by jasonlotito on Friday January 13, 2012 @08:16AM
(#3460401)
Broadly expanded? Standardized? Please.
I think the nofollow attributes intent was fairly straight forward from the beginning: to designate links that should not be accorded attention in search results. In 2005, this was merely via PageRank. Today, it's recommendations in search results.
Why would I want to see search results that shouldn't be given weight in a search result in a search result? Explain that to me.
Google is fairly clear about this:
http://support.google.com/webmasters/bin/answer.py?hl=en&...
"How does Google handle nofollowed links?
In general, we don't follow them. This means that Google does not transfer PageRank or anchor text across these links. Essentially, using nofollow causes us to drop the target links from our overall graph of the web. However, the target pages may still appear in our index if other sites link to them without using nofollow, or if the URLs are submitted to Google in a Sitemap. Also, it's important to note that other search engines may handle nofollow in slightly different ways."
So, if your tweet includes a link, they drop that link from the post as far as their graph is concerned. And that graph is what makes up their search.
It's not just page rank.