I have to say that all this SEO stuff can be WAY overblown! It has been increasingly true for many sites that I monitor for me to get more traffic from sites that protect themselves from spammers. Let me give you a couple of examples:
On blogs I have found that those that accept comments with do follow links, I have found that the comments can be both off topic, full of fluff, and so numerous that you are lost in the shuffle. However, there are some blogs that use spam control such as Disqus, and there is no way you are getting a link back in the comments. For these, the comments are often fewer and more thought provoking, and you don’t get lost in the shuffle. Instead you get quality traffic. I have met some great prospects this way!
Then take a forum such as SitePoint where your signature links are hidden from search engines. The first thing to know here is that no matter how much you post your link will not be indexed by google! Instead if you post something that someone like reading, they may ask “who is this person?”, and that is exactly the way it should work. Better still, the leads are so much more worthwhile converting far more often.
And in my industry (directories), it is the directories that have a REAL review process that are thriving. Directories that accept any link for a fee or otherwise just don’t make it, and die a slow death. Directories that cover their topics well continue to thrive, because they are worth visiting. In the case of directories some do use no follow, but most don’t. But the difference is there is a “doorway” where people submit, and then there are criteria for what is deemed as quality, as well as guidelines for format of title and descriptions. When there is focus on quality, there is invariably a site (or directory) worth seeing!
I think the web is increasingly moving in this direction. Places that get junked up with links that make no sense, as well as posts full of fluff and low on content, will invariably die a slow death. Places that involve real people writing meaningful content will thrive, as will the people who participate in such places.