It's such a blurred line to draw these days. Children are exposed to much more now than 20 or 30 years ago. A lot of what is common place now would never have been acceptable when I was a kid (Jeez, and I'm only 28!) I think it's a good thing for parents to monitor and restrict what kids are exposed to, and keeping material of an adult nature separate from the regular games certainly would help that.
People can get whatever they want on the internet, and everything has it's rightful place. Porn doesn't need to be on a site like this. I was looking for WAV sound files for my computer the other day, and one link unexpectedly sent me to a porn site. (Bear in mind that my kids often like to sit and watch me on the computer, fortunately at the time they weren't)
I really think it just comes down to each individual's sense of decency and morality.

NO PORN FOR KIDS!