Why do some videos on the Internet have great clarity while others are super bad?

Why do some videos on the Internet have great clarity while others are super bad?

This is a question for religous right wingers who sleep with a Bible under their pillow, Internet video fans who lust after adult entertainment videos, and those who know their way around a video camera:
Some videos on the Internet that were made by amateur videographers have great clarity, a diamond-like quality to them, or even when not in high definition you wouldn't know it because like clean water they're crystal clear. Others are bad videos and look like they were shot with a dirty lens.
Lets say we have two totally different videos that are hosted on the same exact web site. One is crystal clear like mountain air and the other other is so bad a quality you run to hit the back button on your web browser so you can move on to the next video. In the scenario I just gave, why is one video an eye-pleasing, user-friendly, picture-friendly winner and the other a loser?

What caused the bad video to turn out bad?

Remember this question pertains to videographers who are amateurs (regular people like you and me) using the latest video camera out on the market as opposed to pros who work for movie studios.




EXAMPLE OF GOOD CLARITY:
http://www.youtube.com/watch?v=8vAhbsTaj_s&playnext_from=TL&videos=QHGkIcbv8Og
http://www.youtube.com/user/AcuteAnalogy#p/f/93/Lm5aGhrzrVk
http://www.youtube.com/watch?v=Lm5aGhrzrVk&playnext_from=TL&videos=4xAzQkPjNOI

EXAMPLE OF BAD CLARITY:
http://www.youtube.com/watch?v=GbKXqgGGyoo&playnext_from=TL&videos=b1aqjv2948Q
http://www.youtube.com/watch?v=qYYnf4-4-GQ&playnext_from=TL&videos=9UJCs5CLEC8
http://www.youtube.com/watch?v=ZM676yGD_5w&playnext_from=TL&videos=v-CXTubTKQI

Originally posted by Handlebar:

Remember this question pertains to videographers who are amateurs (regular people like you and me) using the latest video camera out on the market as opposed to pros who work for movie studios.

Except those videos you call bad clarity clearly came from a fairly cheap cellphone or webcam or some such. A more expensive webcam or a cheap P&S would already produce better quality, albeit not necessarily higher resolution. The first one you call good clarity looks pretty close to what my P&S would produce. The first one you call bad clarity was probably a badly adjusted P&S/a bad P&S. At any rate, a P&S is for photos, a dedicated videocamera like this would without a doubt produce a superior result.

Edit: Point in case, a video created with that camera. Compare to My 4-5 year old relatively cheap P&S (6MP for photos, 640*480 for videos).