Personally my impression is that the developers will generally oppose pornography showing up in the main feeds by sorting out appropriate tags and downvoting mis-tagged posts. I can definitely see alternative UI's popping up for a whole range of different "interest groups". It's only a matter of time before someone builds a sleek UI at steemy.xxx, or something like that, since the Steem protocol effectively provides a seamless way to both identify 'good' content, while rewarding it at the same time. However I still have the impression that it will generally be shepherded to a back corner of steemit.com, especially because we're trying to still establish the integrity of the platform.