Robert_Charlton - 8:53 pm on Oct 5, 2012 (gmt 0)
I don't think you can assign a number to it. I have linked to a conversion page from almost every page on a site with no ill effects, but I did it quite prominently, from a "Buy" button, and with no intention of manipulating anchor text, and no intention of hiding the link.
I've also used inline "contextual linking" to provide references or footnotes to appropriate pages, but I can't imagine where every instance of a word on a site is worth linking.
I'm guessing that you want to boost rankings for "widgets". Conceivably, this may fail simply because it might be like trying to pull yourself up off the ground by pulling your shoe-laces. It depends on the particulars of your site.
Inline contextual linking is likely to help with SEO primarily on the kinds of sites that have direct external inbounds to the linking pages. It needs to be done in moderation and only when appropriate for the user, and it's likely to hurt if you do it without thinking about the user and the appropriateness of the link. I think the links also need to be clearly visible as links.
Take a look at these two discussions....
Introducing heavy internal linking to well ranking site
Static text links issue
To repeat what I said several times in different forms... "the most simple explanation I can give to guide you regarding contextual linking is to use it only to help the user."