Hacker News is a site that is crawled very often by search engines. Even though outbound links are nofollowed, the search engines still follow them and count them as links into a site (they just don't pass pagerank). So the theory is that if I post a spam link on Hacker News, if it stays up for an hour before being flagged, that should be enough time for search bots to crawl their way back to my site.
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Hacker News is a site that is crawled very often by search engines. Even though outbound links are nofollowed, the search engines still follow them and count them as links into a site (they just don't pass pagerank). So the theory is that if I post a spam link on Hacker News, if it stays up for an hour before being flagged, that should be enough time for search bots to crawl their way back to my site.
I just asked Matt Cutts about this and he says nofollow links don't do spammers any good at all.
Remember, he doesn't speak for Yahoo and Bing...
And even for Google, there is evidence that nofollow is treated differently depending on the site:
http://www.seomoz.org/ugc/using-twitter-as-a-sitemap