Y'know, it's strange. After spending so much time on the chans, ED, and so on, I really can't give a definate answer to this question. I don't think that I've ever been really "disturbed" by something that I saw on the internet in the shock value kind of way, not that I can think of off the top of my head.
Except the close-ups of spiders on Wikipedia. Man,
fuck spiders.
I guess stuff like this:
Heronblade said:
In terms of intellectually disturbing, well, this:
http://www.landoverbaptist.net/showthread.php?p=736012#post736012
might count as "disturbing", because it's certainly off-putting...
EDIT: (I know that it's not serious, but there are people who actually act like this. I'm just using the link as an example)