You raise some excellent points and I very much agree with much of what you state. The reason is because my point is not
that link quality can be pinned down to traffic. That is not what I posted nor suggested. ;)
I am pointing out that it is an important one that can be used as a "quick" and "fairly accurate" measure to determine whether or not to dig any deeper. Traffic is generally
the symptom of a healthy website. I agree there are more things to look at but if you need a quick snapshot to determine whether to dig any deeper, then traffic is a good starting point
Despite the low traffic, you can bet the link would be passing high trust rank & consequently help in rankings too.
That's actually like .edu pages. There is an industry around high priced .edu links that is built around this idea of trust and that .edu pages have something extra to pass along. But I believe the advantage of .edu type links has been exagerrated.
The only advantage of a .edu link is the likelihood that there is an absence of negative signals
. The trust test, in my opinion, is about whether or not your site gets dumped into the spam bucket or not. I think the issue of trust and relevance are distinct.
1. Big muscles are a sign that someone works out. Similarly, traffic is generally a sign that a site is relevant for it's niche. It's generally (but not always) a reflection of the quality of it's content and many other positive signals.
2. Traffic is a sign that a site is important. It is important because quite likely there are a lot of sites linking to it. I bumped into a blog with a small amount of PageRank, around three, maybe even less. Their advertising rates were pretty high and I thought maybe they were overreaching. So I checked it in QuantCast and the traffic numbers were high. I then did a backlink search and a search through Google News, Google Blogs, and Google Images- That site was being cited in a lot of places.
Clearly, traffic can be manipulated and it's important to know where the traffic is coming from. Not all traffic is equal. But in my experience the low quality traffic is an exception.
3.Traffic is not necessarily a sign that a site has been SEO'd. Aside from highly competitive affiliate niches, there are many successful sites in a wide range of niches rank well because their content is excellent, their authors are authoritative, and because their site looks good- despite a malformed title tag, despite poor optimization.
4. An association site is great and their links are useful. But an association site that has little traffic is itself diminished by this fact. If you have examined association sites then you will know what I'm referencing when I say that low traffic association sites are generally regional ones, and those sites tend to have relatively few link citations.