I had a long entry written about this, but I'm not going to publish that.
All I'm going to say is this:
Did you know that if something is published online in a blog, a website, etc., and it's an original piece of written work, it's considered copyrighted by the author? Even if it hasn't been registered with the U.S. Copyright Office, it's considered to be copyrighted.
Did you also know that if you take text from someone else's website without permission, your ISP can take it down if the author requests them to? Most ISPs don't want to be involved with any kind of copyright lawsuits, so they're very responsive about removing offending text, and sometimes entire websites.
I know this because I've had people copy my text, and while some changed it or removed it when I requested them to, others didn't. Their ISPs did, though.
So for all you lazy plagiarists out there, start doing the work yourself and stop stealing from other people. That is all.