For example:
- More time users spend on a page indicates it's more relevant
- More high quality inbound links indicates higher quality content
- Content seen as spammy are considered can lower page rank
The fact is that Google don't discriminate based on the rules they set out within their algorithm. When Google say their algorithm does the choosing, it does, but it's the same algorithm used across the whole internet, giving a fair competitive landscape. That's the theory at least.
Don't get me wrong, if I'm looking for the Apple website, I should absolutely get Apple.com first in Google, and not a medium-sized blog talking about Apple. So relevancy should matter most.
However, I fear that they are ranking bigger sites and bigger brands above more relevant posts from medium-sized, sites, too. And that I don't like. Give the little guy a chance, especially if his post is of higher quality.
And no I don't think that if the big site's post gets retweeted 100 times and the medium-sized' post gets retweeted 10 times, it should matter much, because resharing is just a side-effect of being big and having a big audience, and I think it's less about the "quality" of the post.
Google ends up promoting bigger and bigger sites at the top, while downranking the smaller ones, who are impacted negatively by a lot of factors (smaller age, fewer backlinks, fewer reshares, etc).
So I guess my point is, on-page "performance" (for lack of a better word) should always count more than off-page performance.
Moreover, very frequently a little guy has content on bigger sites and enjoys traffic from being integrated into the bigger site ecosystem. Reasoning about search engine result pages is hard because it is a very complex system with multiple various parameters that are factored in.
However the algorithm is based on hundreds of metrics, and is highly discriminating. In addition, Google uses human raters to determine what a good quality result is. This is fed back into tuning the weighting of the metrics.
Therefore, the biases and judgements of these human employees will be reflected in the results.