How to look up the "default passwords" on the web?

Youtube Video: "Learn the Default Password for Every Network Router!"

To save time, you can fast forward the video to 0:21 ~ 0:24. The web site mentioned is http://routerpasswords.com/

This video at least teaches us 2 lessons:

1. If we forget the "default password", we can look it up at this site.
2. We must always change the "factory default passwords" for any devices exposed on the Internet. It would be quite easy for malicious intruders to look them up at the same site.