fb:21-plus – Pornography coming to Facebook?

I noticed a rather controversial tag added to the Facebook developer’s wiki today. The tag is called fb:21-plus. From the documentation, fb:21-plus “Restricts content to users who match the ages.”. Here’s an example of it’s use:

Oh la laBarney?

The only use of this that I can see is for the production of more mature content. Does this mean Facebook is going to become a haven for pornography? Facebook terms of service says one cannot:

upload, post, transmit, share, store or otherwise make available any content that we deem to be harmful, threatening, unlawful, defamatory, infringing, abusive, inflammatory, harassing, vulgar, obscene, fraudulent, invasive of privacy or publicity rights, hateful, or racially, ethnically or otherwise objectionable;

Is pornography one of those things, and is this an area Facebook really wants to get into? What are your thoughts?

UPDATE: I just realized there is also an fb:18-plus tag just added as well (why not just do an fb:age-above tag?)