It really depends on who your target audience is…
Keeping them together:
- Pros:
- It’s the real you.
- You won’t need to worry about what goes where.
- There’s always something (off topic) to blog about.
- Cons:
- Narrow-minded readers are exasperated by diversity. Especially if some of the topics you blog about can be controversial. (And narrow-minded readers are many.)
- It’s harder to monetize, if that’s the stuff you’re into.
Splitting them on multiple sites:
- Pros:
- Readers always get on-topic content.
- The signal to noise ratio will probably seem higher to newcomers.
- Fickle readers don’t run away when they disagree on topics that may be controversial.
- It’s easier to monetize, if that’s the stuff you’re into.
- Cons:
- It’s not the real you.
- You’ll eventually grow tired of behaving like a schizophrenic.
- There isn’t always something on-topic to say, so the rate of posting may occasionally suffer.
- Your readers’ interest might fade faster: there’s only so much you can read on a topic before you move on.
Tip: if you end up setting up multiple blogs, consider maintaining a twitter account or a brain dump blog, for stuff that fits nowhere.