Looks like a good opportunity for someone to build something tumblr-like strictly for NSFW content that encourages people to build connections like tumblr does (or did)
Most sites, including community sites, built explicitly around NSFW content are, for lack of a better word, gross. I want little to do with them and most women I know want even less to do with them. It's hard or impossible for them to have any taste.
One key to the success of NSFW communities on Reddit (like GoneWild) and Tumblr may be their "dual use" purpose; they tend not to be completely gross (though there are obviously exceptions) and consequently they also attract women.
The challenges are two fold, one if you put a stake in the sand vis-a-vis porn and nsfw content then you may find yourself without an exit strategy. That is just another way of saying that you will want this new thing to be self supporting (unlike the original Tumblr) which might mean ads earlier rather than later. But it also might mean a membership fee of some sort.
That said, yahoo's probably trying to remove NSFW content to fill the ad spots that they're invariably planning on throwing down everywhere, so I'm not sure how well an indexer would do on its own.