Apparently there was some big changes in the Google Algorithme recently. I wrote a post months ago about how to use the nofollow attribute for internal linking (PR sculpting): be aware that this is apparently changing and the use of NoFollow internally does not seem to be advised or accepted by Google.
See below a pic [...]

Quick reminder: NoFollow is an HTML attribute used for hyperlinks on a page. The link remains a text link but Google Spider won’t follow them, or won’t give credit to that link for rankings (the link juice is not passed). Google has set up this originally to fight against spam. Indeed, links from comments on [...]