I don't think this would be good for Longecity. Survivalism is associated in most peoples' minds with the lunatic fringe, which we have enough trouble with already. If we want to raise our profile as a serious site, I'd stay away from this one. Maybe we could have a survivalism thread in the Global Risks forum. That way we could have it for all who are interested without giving it too high of a profile.
Overall I agree with niner on this.
The major cons are:
1.) Tends to take away from main focus of the site.
2.) Diversion of resources.
3.) Reputation and the lunatic fringe cited by niner.
On the pro side:
1.) Attract new readers.
2.) Treat survivalism with a "Longecity" focus, for example pointing out that "maybe that bucket of beans and rice needs a more balanced nutritional focus".
3.) Possible new revenue from ads and sales.
At least that is the view from this noob...