Wherefore art thou blogging?

Monica has an interesting post on her blog today (doesn't she always?) about author blogging. What should author blogs contain, or not contain? Who cares about authors' personal lives?
Obviously, a blog, anyone's blog, is a method of communication. What's not always so clear is who the intended audience is. I suppose you could group the possible readers of my (or anyone else's) blog into four categories.

a) Me myself. I know navel-gazing is not attractive, but JD Salinger has been writing for his own benefit alone, as far as we know, for years. I've already found my own blog useful as a source of reference (eg. how bald my new chickens were when I got them), and I suppose that writing a blog is still writing, and thus a good thing for a writer to do, even if not words on the page (or screen) towards any work of fiction. And anyone who's writing a blog regularly is spending some considerable time on it, so it's to be hoped they're deriving some pleasure from it, which in itself is a Good Thing. Still, if it's mainly for myself, a diary would be just as convenient.
b) My family and other people that I have real-life relationships with; people I have physically seen or spoken to. My older daughter, who's ten, is about the only person who I can guarantee will read everything I write here. The fact that she thinks my blog is cool enough to show her friends is gratifying (and given my dress sense, I surely need every competitive advantage I can get in the coolness stakes), but obviously limits the content to some extent. Given she reads teen magazines, I don't feel I need to watch my vocabulary *too* much, but there are some things I'm not going to say on here with her noting down every new swearword. But given she loves reading my blog, and likes the personal stuff about our lives, I'd be silly to alienate the core readership by never writing anything about our animals and suchlike.
Next most loyal reader is probably husband, who reads my blog when away on business, which is about a quarter of the time. Again, the personal stuff is good for him; saves me writing separate emails, which his work server often loses.
As for other RL people, few of them know I blog or would care anyway, but I'm not making great efforts to hide my RL identity for this blog, so I'm not going to include anything I would really hate real life people to know. Not that I can think of much in that line, anyway.
c) Members of the blog community who might visit my blog. Some of them have, and I'm grateful. Obviously some things I write will appeal to some people, other things won't. Meljean is currently running a hilarious series of posts in which she revisits 1980s romance novels that she read as a child. I love these posts and can't wait for the next one, but it seems from Meljean's blog that she's also very interested in shoes and in Batman fanfiction. I'm not interested in Batman at all, let alone extra words about him, and shoes for me are things you put on your feet to go places, often, in my case, with lumps of chicken shit on the soles of them. Am I adult enough to check Meljean's blog and just read the bits I like? I think so. Are other people going to do the same for me? With any luck.
d) Random people who are here by mistake. Well, I needn't worry about them.

So,I think Monica's summed it up: you have to do what you feel is right for you. Monica doesn't want to talk about her private life on her blog; that's her choice, and she certainly doesn't need to do so to make her blog interesting, but if she chose to go into more detail about the way she writes, as Holly Lisle does, or used more specific examples from her own life when discussing race issues in America, I am sure there would be plenty of people keen to read it. When Allison Brennan (oh, how I hate typing those two 'l's in Alison!) wrote about juggling five children with writing, I was gripped, and now know I can't use two school age children as an alibi for my continued procrastination. That's an issue that touches my own life, and so I'm interested in it. I'm interested in the personal lives of just about all the people at about the same life-stage as me: those much older or younger, not so much.
There are some blogs among the frequently-listed ones that just don't float my boat at all, but others obviously like them. And surely that's another of the great benefits of the blogosphere - that you can tap into the thoughts of those who share the same interests, concerns or sense of humour, no matter how different you may be in other ways.

All this started with the question of whether author blogs are a good idea. I can't see why they wouldn't be, unless, as Monica says, they are clearly self-promotion and no more. I can't think of any authors I've discovered in the local bookshop whose blogs I've bothered to find. I seldom even look for author websites, if I come across the book first. But if I've read the book and liked it enough to read another by the same author, why would I be deterred by even a crappy website? On the other hand, if I come across the blog or website first, and therefore buy the book, that's one more sale the author would never have made otherwise. I've bought three books this way in the last month, and I'll do a three-way review when I've read them all.