The Power of Content theory states that each page must have some link juice value. It's rather like a can in fighting where every page no matter how many links go out(how bad a record) gives some benefit to the page it's linking too. I get a lot of random links but google still shows them in webmaster tools. I get a lot of random links from the same sites like righthealth and kosmix for my quest for height blog. Usually, when I search for my blog whichever site is the double listing for when I search for "quest for height" is the site with the most random links.
If Google stopped counting links from the same C-class ip per domain then why are people building links to their ezine articles or hubpages? The logical conclusion is that the C-class ip thing is by a ratio and that the search engines expect you to have a lot of different links from a lot of different C-class ip's. And what about internal links?
What I've done is to adapt to what I see in google webmaster tools. Google says I have 520 links to my domain in my main blog but only shows my 160. However, for the rest of the pages on the site it shows me all of the links. This says hey I need to build links to the other pages of my site. Whenever I hit a plateau on domain wide links showing up, building links to the internal pages of my site seemed to help. It could however be a sandbox thing(where domain age affects how many links are counted) but the counterargument to the sand box is news stories which get a lot of links very quickly. Usually they are not whole new sites though but are part of an already trusted domain.
Basically, my view on the C-class ip thing is that Google tells you when it counts links or not. When links stop showing up then you get links from a new source. Google Webmaster tools says that anchor text is valuable so if the anchor text is showing up that means it's a good link(comment links show up). The amount of time that it takes for the anchor text of a link to show up correlates with how valuable that link is.
I think the whole C-class ip thing is over-exaggerated and mainly designed to sell products. I mean if you're making mini-sites that are one page with exact matching domains then maybe the C-class ip thing matters more but I don't think so for larger sites(I think you can have a very large percentage from one domain no problems as long as you vary anchor text and page linked to).