If you write anything (and I do mean anything) but have never given copyright much thought, do yourself and everyone else a big favor and read Brad Templeton’s articles, A brief intro to copyright, and 10 Big Myths about copyright explained.
"Oh, but I’m just a little blogger," or "But I just write reports/proposals/e-mails at work. I don’t need to worry about copyright stuff. That’s just for publishers, isn’t it?" Believe me, you DO need to worry about copyright laws.