If someone adds the rel=â€nofollow†to their site, why should Google even bother to honor it? With so much in-secret already, I wouldn't be surprised if Google doesn't read and utilize links affiliated with the rel=â€nofollow†tag.
The rel="nofollow" mechanism was originally developed by Google and Yahoo! to fight BLOG SPAM. Links that include rel="nofollow" do not pass link value to the target site and for Google, they also prevent the link from being counted against the host site for violating Google's guidelines, and Google has been recommending using this mechanism for advertising links as one of three or four methods of handling ads and staying within their guidelines. While I doubt that it happens, whether or not a search engines follows a link marked rel="nofollow" to discover pages is pretty inconsequential. If the target page is on your own site, you have simple tools to prevent it from being indexed if that's a problem. And it won't be indexed for long if there are no plain links (ie. links that are not marked with rel="nofollow") pointing to it. Pages with no plain links pointing to them are rarely indexed at all, and soon drop out of the index if no links are discovered within a short period of time.
????? errr that's kinda the point of nofollow. Any link marked up with rel="nofollow" is not given weight or even 'followed' by google. Why whould they honour that, because they are the ones telling us to use that for paid links etc....
Uh, maybe because they created it??? Or if not that, how about to fight spam and improve the quality of their index. Why shouldn't they? It's not exactly like they owe anything to the spammers.
"errr" uh, because what if there was a link - with no weight as you say - that Google had never encountered before? And suppose that link was more text rich and diverse than other related link? That's part of what came to mind when I wrote the question. But it maybe that Google experimented and learned that such small discoveries were fruitless. Anyway, thanks for the answers. I hadn't read about any of the history or roots of that.