Humor is most certainly subjective. What might seem hilarious to one person, will fail to amuse another. But it's really a testament to the human race that video after video of a kid screaming in a high pitch voice is considered funny, and when I say video after video, that's pretty much all there is to it. Once you've seen one video of Fred, you've seem 'em all.
Being on of YouTube's most subscribed users, Fred's unfortunate popularity doesn't end there, as he even spawned his own feature length film with a sequel currently in the works.
It makes me wonder what will happen when these videos are possibly rediscovered by future generations. It's almost quite scary to think about.