Mouseover video playback its kinda crappy when your scrolling, if your mouse cursor is crossing over several videos you just keep hearing too many random sounds. Also since everything is recorded at different volumes it makes my ears bleed.
Now since these videos are user generated they are all recorded with various levels of quality. If your mouse moving through ones that are poorly recorded that split second of playback sounds horrible.
You can simulate the effect if you visit https://giveit100.com/@Benjamin and goto the day 18. If your move your mouse past it you'll hear some really bad static for a split second. Now imagine if all the videos are like that while scrolling down the page, it's a pretty horrible experience.