One of the most common errors I have seen in the SEO world when analyzing a campaign is to evaluate isolated elements trying to
assign a cause - effect relationship, and that causes certain distortions in their conclusions.
I will be more specific, I read many threads and comments about Google, and penalties asking for isolated items such as how many backlink of .edu the competition have, or how many high PR backlinks are etc... this is not wrong, but it is not right either, what you need to start doing is broaden the vision and start analyzing the patterns, look for patters more than individual elements, because that is exactly how Google works, analyzing patterns and creating profiles based on that, when you can't analyze each one of the elements of a population what you do is to take random samples of them and you keep taking randome samples to create patterns and have a better picture of the total elements of the popularion without the need to counting each one of the members you want to study.
See what type of questions most of the people ask: How many backlinks should I create?, my competition have 5000 spammy backlinks and it is at the top why?
To ilustrate the point better I will use what is called the "bold men paradox" it goes like this:
"How many hairs should a man have to be considered bold?"
if you apply it to the world of SEO the question can be asked as: how many bad backlinks should your site have in order to be penalized? or
how many backlinks should your site have in order to be at the top?
How many backlinks from the same source should I have in order to be penalized?
My competitios have 5000 backlinks and I have 10000 why am I not above them?
and so on and so forth....
In order to "solve" the bold man paradox what Google does is to follow patters, instead of asking the question of "how many hairs" the question they ask is :
"what is the pattern on his hair?, is it loosing more hairs than it is growing?, are the hair loosing at the top of their heads?"
If the patterns show that he is loosing hair faster than he is getting new and besides that it is from the top, then yes this men may be bold...
Same happends with the backlinks profiles it is not about specific elements, it is more about patterns...
Google does not see just how many follow or no follow links you have, it looks for patterns... that is why you may create a post today, spam 10,000k links and start ranking, BUT after a while your ranking is gone, because they saw the pattern, it is not that they can't differentiate between a good link and a bad link, because there are no such things, BUT they can identify patterns... spammy patterns and non spammy patterns.
That is why the real question you should ask is not how many links, or what type of links you should have, but more like... what type of backlinking strategy should I implement in order to have a pattern that Google accepts.....
Probably the answer to the question it is more complicated and that is why people prefer to answer the wrong question than asking the right ones.... and may be that is why SEO is DEAD for many people, because they keep asking the wrong question.