Changing them is better than blurring. There are methods to unblur images and video to see the underlying information and I would not rely on it as a way of obfuscating things. But not using a live, on-the-web server would be even better.
Just make sure that you change stuff prior to posting the video. If you post the video and you haven't changed things, you've greatly increased the risk of an attack. But I think you know that! :-)