How often do cameras mess up?

For all you amateur and professional filmmakers out there.
Let’s say you went on vacation and decided to make a video blog. Let’s say each video is about 5 minutes long and you took around 500 videos.

How many of those videos would have an audio or
video anomaly? (like static, audio cutting out, video glitching, etc…) Even for a split second.
I’ll say from any kind of camera (I don’t know about the various kinds particularly well) 1 in 100? 1 in 500? Even less?

I will also say mostly normal taping and some movement. So no shooting complicated things, moving roughly/quickly, or in bad environments. (Of course with those circumstances something can go wrong)

And for those with first hand experience with messed up video/audio, what was the nature of the anomaly in the video? Do you know what the cause was? (camera crapping out, forgot to plug in the mic, don’t know?)

The reason I ask is that I have been watching these videos about some ‘paranormal’ thing about the ‘slender man’. Most of it is messed up video and audio. The poster says he sifted through tons of video to show specific anomalies he saw in the videos. I KNOW that it’s total bs, but still enjoy the mystery.
http://www.youtube.com/user/MarbleHornets

I just want to know if most of the anomalies (problems) in the videos could actually happen through normal taping, the odds of them happening, and if some of the anomalies could only produced specially.
here’s some things I’ve seen: Video split horizontally, audio cut out to static then coming back, video suddenly getting all pixelated with the camera not moving then clearing up.

I don’t care about the paranormal end of this. I want instances of a video getting messed up somehow, what it was, and why it happened. (The battery was dying, someone smacked the camera) And of course there is a possibility it’s all special effects.

Go ahead and have some fun. But I’d really like to know the first hand experience with video problems from those of you who’ve made any sort of film.