Ok, so this is just something I noticed, it isn’t based on any tests or studies, it is just from observing the SERPs and link profiles a lot, that and what I believe is common sense.

Ok so lets look at things from my perspective, say I would like to get my good friend and colleague, Paul Carpenter, to rank for ball spoons (which I’m sure he will soon).

Lets say I wrote blog post after blog post with the keyword “ball spoons” linking to his homepage, now I don’t know about you lot, but I reckon Google might just cotton on to the fact that all these anchor text links are coming from the one blog and treat them as “1 vote” for relevance.

Reading some of the old Google patents, one of them mentions that they calculate page rank and relevance separately, and then combine them together somehow. Anchor text links are a relevance factor – so isn’t it possible they only consider one unique anchor text link to a URL from a domain?

e.g. If I did 3 blog posts with “ball spoons” linking to Carps, Google would calculate the page rank passed for 3 links, but only the relevance from the anchor text once. Or would they count it 3 times?

This might explain why I’ve not seen much increase from using the same blogs to link to the same URLs with the same anchor text – but then significant jumps when I get something as simple as a reciprocal link.

I have no idea if this is correct or not, and I have tried to think up tests for it – I even attempted one, but unfortunately it failed at the first hurdle (I couldn’t get all the URLs indexed). Does anyone else think this may or may not be the case? Or does anyone have any evidence pointing in either direction? Or can anyone even think of a way of testing or refer me to any previous tests?

Update: In SEOMoz’s 2009 Search Ranking Factors, the highest factor was anchor text and the third highest factor was diversity of links. This theory could possibly explain those ranking factors.