One blog or many blogs?

A fellow author recently asked if he should have one blog where he consolidates all of his interests, or different blogs for his different audiences, since they are pretty disparate topics with little overlap.

It's a dilemma with no single right answer.

One point of view says that the most loyal fans come about on single author blogs. That is, Brad Feld has a rabid set of fans, while something like GeekDad, with a dozen different bloggers, won't ever be able to inspire such a loyal group of fans.

The thing about single author blogs is that they almost always shift topics over time. A person's interests change year by year, and five years later they may be onto an entirely different set of topics. Yet it still works. We like to follow people.

By comparison, a topic oriented blog is just that: a topic. The reader's interest in that topic may wane, and they'll stop following. I'm no longer reading TreeHugger or the other environmental blogs I used to read. Yet I'm still reading Rebecca Blood, a blogger I met once and emailed a dozen times, and who has some very different interests from me.

My thought is that over the short term, topic-specific blogs are better. But over the long term, just expressing all your interests in one place is better.

I'd love to hear your thoughts on having one blog or many.