Charliehall and Yekke2:
What I was referring to is the one (and here I apologise for not finding the correct loshon or maareh mokom, I simply cannot be bothered) that says that one who walks in a place were they are likely to be exposed to immorality, even if they do not look, is called a rosha. This applies to the internet too. And many contemporary Gedolim call being alone with an internet enabled device yichud. I was not saying the ban is by itself a gezeirah, simply that it ties in to an existing one. So you may pick either of those.