Well, I think there ARE some hard and fast rules. Like, you know, be interesting. Or communicate clearly. (Even if you're disobeying grammar rules, you have to be clear!)
And the rules change depending on who you're writing for. Just for yourself, in a journal? Go nuts. For friends and family? You might want to tighten things up a bit, so that people enjoy it. For publication? That's a can of worms that I don't even want to open today!