One of the things we did when we saw no-follow links having a really high correlation was we went, well that’s just weird. Maybe what’s going on here is that no-follow links and followed links have a high correlation with each other, and in fact, they do. If you have lots of no-follow links, you tend to also have lots of followed links. So, that makes sense. All right maybe that’s all that’s causing it. But then there’s this one weird, weird data point – well, there’s several weird ones – but there’s this one weird data point around the percentage of followed links having a negative correlation, kind of a strong negative correlation with rankings, which sounds weird, but it suggests that websites and web pages that don’t have any no-follow links aren’t performing as well as those who have at least some or some reasonable percentage of them.
This paragraph caught my attention enormously, mostly because I’ve always been of the opinion that natural backlinking from a variety of sources is the best way to do off-page SEO. I’ve always thought that a healthy mixture of noFollow and doFollow links were important, otherwise it’s pretty frickin’ easy for search engines to notice that you’re trying to “game” your rankings. This is also why my automated social media service, SocialAdr uses a mixture of noFollow and doFollow social media sites.
Aaron @ SEOmoz sums it up well when he adds:
What I think that’s happening is that people who do natural things, normal websites, this is not normal. It is not normal to have a website that only has followed links. It’s almost like, man, you must be doing something funny because normal websites earn links from no-follows. They get linked to on Wikipedia, which is no-follow. They have blog comments that people leave and point to them. Those are no-follow. They have social media profiles. Almost all of those are no-follow. People tweet about them. Those are no-follow. There are all of these no-follow links that exist from sort of good places on the Web where you would naturally be mentioned if you’re a good website.