blogging motivation factors

The idea I want to ask you about is what motivates you to write about a certain topic:

* Audience needs - Many writers will tell you they write for a particular audience but how far up in the priorities and idea generation process does the audience come? For an Authority Blog I think this is a key success factor but I don’t think every writer thinks about what an audience needs first. There are a few blogs and newsletters I think fit, or appear to, I am thinking Steve Pavlina, Adam Kayce and Sean D’Souza. I aim for this one but at least half the time I fit into the following category …
* Existing Expertise - “Write what you know” is common advice to writers. I have a theory that many people select from their personal collection of possible topics those that will resonate with their audience. Their own experience comes first then their readers are brought in as a filter. Am I right? I am thinking most blogs that I follow fit this mold, particularly “been there, done that” blogs such as Shoemoney, Strobist.
* News Reporting - Do you write whatever is newsworthy today? Techcrunch and Gizmodo fit into this category. If you follow the news then there will be little control over topics, though you might be able to reduce down possible stories to just the ones that are most interesting. For example on my photography blog I only report new cameras that I know my audience will want to know about.
* Follow Mood - Probably more for personal columns and blogs, it is rare outside of those venues you have the freedom to just write whatever comes to you on any topic at all. My personal blog fits this, I have no topic selection at all other than to record the random thoughts that come to me. I wonder how many of some of my favorite reads fit this too to an extent, like Darren Barefoot and Aaron Wall …
* Entertaining - Possibly you have only entertaining your audience as your criteria. Any topic goes providing it is fun, interesting or humorous. Scott Adams blog fits this criteria, as do online comics like Penny Arcade and What the Duck. They might follow themes (”philosotainment”, Games and Photography respectively) but the primary selection process is to entertain.

Do any of these fit you or am I way off track? Please select which most fits from the poll then tell me about it in the comments …