Not a parent, but I think the problem with kids watching pornography is that you're basically letting a random person teach them what sex is. If a kid who's just beginning to get curious about sex stumbles on hard-core BDSM/rape fantasy sites, it's probably going to have some sort of impact. (I picked an obvious bad-case scenario, I'm not saying it's always like this, or that it'll certainly traumatize them, etc., etc. I just wouldn't want my kid's first experience with sex to be a video of a gagged woman being whipped.)
> And is not like porn randomly plays itself in the browser, you have to use explicit sexual words for Google to respond with links to porn sites.
I was going to come up with an example where little Billy is searching for his uncle Dick, but most of the results are about Dick Cheney, which is arguably more frightening than pornography.