All links provide value unless the are on "traffic exchange" sites, in which case they are against Terms of Service for BOTH Google, and Hubpages.
All other links provide value.
Here is the thing: You seem to be asking about DIRECT traffic...but when I bookmark something on Yahoo Bookmarks, Delicious, or Google Bookmarks...I am NOT looking for traffic from those sites.
Why do I bookmark to those sites if they give me NO traffic from the site?
Indexing....When I hit "publish" I want my hub indexed right away, and the best way to do that is to spit out some backlinks on different kinds of sites.
Search engines wind up seeing the link, categorizing or indexing the link, and making it available for search results pages for person searching for the thing I've just published, or something relative to whatever I've just published.
So yahoo bookmarks and delicious may never ever EVER give me direct traffic, I know for a fact that they help get me indexed with Yahoo Search Engine.
Yahoo search engine is very much a minor consideration, but it helps too, of course.
You don't even care if anyone from those sites views your hub!!!!!!!! You don't bookmark for that reason!!!!
Also - the "my account" and "traffic sources" portion of Hubpages is very insufficient for looking at your traffic stats.
You get much better results for traffic on each individual hub by going to individual hubs, and clicking "stats."