If YouTube is the greatest thing about the 21st century thus far, Wikipedia is the worst. Both have similar effects on my tendency to follow any train of thought to whatever logical/illogical conclusion, which in my more formative years resulted mostly in a lot of daydreaming. Daydreaming, naturally, is only as entertaining as your imagination and/or lack of interest in whatever you're supposed to be paying attention to (school, church, relatives), and no matter how creative you are or how boring grandpa is, you're going to snap out of it sooner than later. YouTube and Wikipedia, on the other hand, take (advantage of) your idle, wandering mind and supply it with a virtually endless series of additional distractions, some directly relating to your initial train of though, some not even tangentially having to do with anything you give a half of a tenth of an ounce of a fuck of a shit about.
My attention span was shorter than that of a mosquito long before the internet. I never took Ritalin when I was a kid because I heard it made your nipples fall off, so I told my folks "please no" and we all suffered together. Now I'm in my 20s and my apartment's full of mosquitoes (I try to kill them or at least shoo them out, but they're just too focused). I'm a grown-ass man with shit to do, but not if YouTube and Wikipedia have anything to say about it.
Now: I love YouTube. Love the hell out of it. Best thing to happen to me in forever. Don't own a TV, don't need a TV. Wikipedia? To hell with it. Hate it on general principle (I'm not even going to get into how much I hate it for things like forever destroying the power of myth, or how much it creeps me out that there's already evidence of large corporations editing pages to suit their own needs (music-specific example here)), but for the purposes of this ramble I hate it for how much time I lose to it, reading about things that didn't used to matter to me, that still don't matter to me, and didn't really matter while I was reading about them. Both things are so similar in the time-waste regard, but here is the main difference:
YouTube is entertainment; Wikipedia is information.
If I'm going to be wasting my time on something in the manner of an idle daydream, I would rather it be entertaining than informative. Especially if it's information about the bullshit I tend to read, which is probably 5% science and nature, 15% history and politics, and the rest entirely meaningless and useless sub-trivia (tune in tomorrow-ish as I relate how I accidentally discovered they're making an Alvin and the Chipmunks movie and subsequently became so furious with pop culture I shit blood out my dick). Yeah, yeah, nobody puts a gun to my head and makes me read this stuff, but for chrissakes, I go and look something up (in the previous example, information about a David Cross standup special) and natural human curiosity makes me become an active participant in the downfall of my own evening. With YouTube, someone sends me a link to three guinea pigs fighting over a piece of cucumber (see: below) and shazam: I'm more than happy to give up control of my destiny to a series of cute li'l critter videos, because I'm relatively sure I'm not going to end up three hours later knowing which cast member of the 2001 Broadway revival of Caberet has obsessive-compulsive disorder, and five hours later forgetting which cast member of the 2001 Broadway revival of Caberet has obsessive-compulsive disorder.*
Look: if I want to watch an old music video or clips from a TV show I used to love or just kill some time, YouTube is incredible. If I want to know something very, very specific, I'll go to Wikipedia, but from now on I need to train myself to treat it like a mad dash into Home Depot to get something to fix a leaky sink; beyond my tendency to go "wow, I've never heard of THAT comic book!", I'm getting sick of how easy it is for us to treat an enormous chunk of the assembled collection of human knowledge as disposable and borderline meaningless.
And when I want to shake myself out of a slack-jawed, glassy-eyed stupor and go "wait, what? How did I get from thinking about my favorite Kinks songs to wondering how turtles have sex?", I want to know that I got there on my own. Just like I did when I was a kid.
*: This fact is make-believe. And no way in hell I am going to look it up on Wikipedia.