Submit whatever you like, the people who enjoy that content will follow you, the people who don't will ignore you. At the moment, I don't think you would get a huge following submitting NSFW content, but that may change as the hubski userbase grows. You would definitely get a lot of ignores from people who don't want to see NSFW content in their feed, and therefore you would not be able to comment on those posts.

I don't think there are any rules about the type of content you can submit - mk, could you confirm or deny? Hubski is all about cliques - people who follow each other and share each other's submissions. If you're serious about starting a NSFW community on hubski, I would recommend getting a few of your friends to sign up and start submitting that sort content as well. It's just like starting a new subreddit, except instead of trying to get subscribers for your subreddit, you're trying to get followers for your account.

Right now most of the users on hubski are all interconnected, as seen here:

http://hiiamchris.com/hubski/hub_graph/graph.html

It would be interesting to see what would happen if more diverse groups of people who like different type of content start signing up. Personally, I don't think my own hubski experience would change much at all, since I would just ignore the nsfw tag and any other related tags.