It absolutely makes sense! Over 10 years ago I started Productivity501 writing on various things I was learning about personal productivity. It has been extremely beneficial as a writing exercise, but it has also given me a much bigger presence on the web. A government agency was doing a background check on me for some contracting work. After they started, the person in charge of contracting called me up and asked how in the world I had time to do everything I had done online. They had done some searches and started finding hundreds of articles I had written over the years, interviews on other websites, people talking about articles I had written, etc. It made a huge positive difference in the way they perceived me.
Regarding not being an expert in some technical field: If you are putting any time at all into learning something, there is always going to be someone coming after you that knows less than you do. Explaining how you fixed a problem or set something up is going to be valuable even if it is very simple and even if you aren't an expert. Do a Google search for "connecting Visual VM to Tomcat 7" for an example of a post that I wrote simply to remind myself how to use Visual VM with tomcat. I am in no way an expert on Visual VM, but many people have found it helpful.
I have a few posts where I've written about a particular problem, forgot about it, and later Google led me back to my own post when I was looking up how to solve that same error again. So even just posting an error message along with a discussion of the details of how you fixed it can be extremely valuable. Think how often you've found an answer because someone else took the time to do the same thing. You probably didn't care if they were considered an "expert" or not.
One last example. Take a look at this article I wrote as an introduction to state machines:
http://blog.markshead.com/869/state-machines-computer-scienc...
I wrote that post to see if I understood the topic well enough to articulate it well. I'm pretty happy with its current state, but, despite all the time I put into it originally, the real work came when it got a bunch of comments from HN readers. If you scroll down to the comments you'll see people pointed out all kinds of problems that I fixed or clarified based on feedback I received. I may not be an expert, but taking the time to write the article, correct it when people pointed out an error, explain when someone thought they found an error that wasn't, and answer questions has given me a much greater amount of expertise than I had before and I'm not sure I could have gotten it any other way.
All that to say, go for it! Don't let your perceived lack of expertise hold you back. You'll find it to be an extremely valuable way to grow.