The purpose of blogging?

I only started with Monday because it was such a shitty day and this whole week was bad. So, now that it is all out of the way I can move on. Gosh, this is a nice way to vent.

Today I had to get up before FI. In fact, he was still in bed when I left. When I got home, I noticed he must have overslept because the dogs had not been fed. So, I take care of the pets. I sit down to read my email and then I'm headed for the gym. Except........I find out one of my computer friends has started her own blog. And I realize a majority of them have blogs. So, I decide to start my own. Did I make it to the gym? Nope. I'm sitting here blogging my shitty week. I hope this doesn't take over my life.

I realize I'm doing things a little differently. As I look at other blogs, I realize their posts usually reflect on one topic, whereas I'm talking about EVERYTHING! Oops. Are there rules on blogging? Should I stick to one thing and keep it simple? Who is really going to read this?
Do I want to tell my IRL (in real life) friends about this? What if I vent about them, or spill some secret? Do I want them to know EVERYTHING??
What if someone I don't like stumbles onto this? Can I keep it private and still have it out there for all to see?