All of the widget refinements (there was like 40) were no followed and if you clicked any of the refinements then they were also canonicaled to the main widget category. Basically all of the juice was going to the main category.
Not sure from this description whether the nofollow refers to a meta tag or to a link. A nav link that is nofollowed is a PageRank black hole. You can't funnel PR with nofollow links... you can only waste it.
With nofollow in the robots meta tag, there would be no link juice recirculation from a nofollowed page.
So, when you say that "all of the juice was going to the main category", I've got to ask "what link juice"?
. If the links to the page were nofollowed, then link juice has been blocked from getting to the page.
If the robots meta on the page has a nofollow attribute, then I think we're getting into an area that we're not quite sure about, which is whether a canonical tag confers link juice from a page... and, beyond that, from a nofollowed page.
If you don't want a page indexed by Google, a much better use of internal link juice is to use the noindex,follow meta tag, with nav links back to the main category. This would keep a page out of the index, but would also allow link juice to recirculate around the site.
Also... important to consider is what Broadway brought up, whether we want long tail. I'm not sure from the example how different the widget "refinement" pages are... whether they are individual products worth targeting, or whether they're subtle product variations (like color and size) that are another level down.
[edited by: Robert_Charlton at 8:41 pm (utc) on May 25, 2011]