Let's say you are a member of X community - vintage cars, death metal, whatever - and your interest in this is completely independent of reputation or profit.

You actively pursue this interest in your free time, and find that many of the problems you encounter have already been solved, and solutions are already available on the internet.

As you develop your skills, the problems you encounter become more and more situation-specific, and you find it helpful to ask questions on forums related to what you are doing.

At some point, you get annoyed at the disorganized nature of the forum. You end up repeatedly linking people to other threads, which are usually poorly formatted, and difficult to find. You decide enough is enough.

You set up a blog. Your only motivation is to solve common problems rapidly - any monetization merely helps offset the costs of web hosting. This is your hobby, after all.

As time passes, your blog begins to develop its own unique "voice" in your community - you have a specific set of problems related to your community that you are very good at solving, and you have built up a significant amount of reference material that others find very, very helpful when they are starting out.

When the blog reaches a certain critical mass, you end up with users who are intimidated by the amount of information on your site. Not everyone has time to browse through your entire archive, but they still want a decent "baseline" of expertise to work with.

At this point, enough people will want a printed version of your content that it wouldn't make sense not to offer it. If the demand for your skill set is great enough, you could make a career off of it.

Professional writing is paid research, more than anything. Why do you need to convince people that the research you've already done is worth reading? Why can't you help people with their own research instead?

Even if your SEO skills are garbage, a basic wordpress install gives Google more than enough information for people to find you when they need help. You shouldn't be writing anything that is already available through a Google search. Why waste your time repeating someone else's work?

If you feel a real need to replace someone else's work, because you feel it can be done better or more completely, why aren't you talking to this person, or even actively working with them? If this really is your hobby, and you really are an expert, why should they feel threatened?

Sorry for the long rant, but I really, really, really find the blogosphere completely disgusting right now.

There should not be competition among people who are genuinely interested in the same topic. Especially on the internet - there is just no excuse.