This topic is always interesting..
I don't believe that you are a 100% correct seomanifest. I would suggest that not every link is 100% relevant or even close. It is more *NATURAL* that people that don't only write about... let's say
marketing sometimes happen to mention it and then point out RalphyBoy's site because they heard it from a friend or whatever (word of mouth is still the absolutely most powerful marketing tool their is).
I believe natural is the key and I also strongly believe in a "natural" mix of both quality links, relevant links and those really piece of shit links like guestbooks, links from irrelevant sites etc. If you have a ratio of 90-100% quality links it doesn't take a genius (or a bot) to guess that something fishy is going on.
It's a bit the same as having 10 000 links in one day. It isn't natural and wouldn't probably occur for a fresh no-name site the same way not every marketer would instantly write about a new marketing site (that google have never heard of).
Imagine we launch a site about Graffitti, it's such a great site that other relevant sites mention it - but if it's so grand and great.. how many NON-relevant sites do you think mentions it and what's the ratio of sites that is purely about 1 thing (or very close to "graffitti" like something about street art maybe) and the sites that is about an array of things like blogs and such? The ratio is probaby 1:10 000.
Prove me and my boring logic wrong and you have done me a favor of teaching me something new.