Even its proprietor says it's not a good thing when you have to join the RareShare social network, but for those suffering ultra-obscure diseases and disorders, it's a powerful resource.

The site, currently building its way through beta, is geared toward those suffering from what the National Institutes of Health call rare or orphan diseases -- those affecting about one (or fewer) Americans in 1500. The term "orphan disease" indicates one so uncommon that drug companies tend to ignore it, but if you're the only person you and your doctor have ever heard of with a highly uncommon condition, the "orphan" label feels mighty personal.

David Isserman was working with a biotechnology company several years ago to build a resource site for adrenomyeloneuropathy (AMN), a genetic defect famous to movie fans as the ailment battled in Lorenzo's Oil. Isserman is not a doctor; at the time he was a marketing consultant, and he's currently a first-year MBA at Columbia. But his name and contact information were on the site, and the requests for help -- or even for just contact with others coping with AMN -- pointed him toward a need that, thanks to liability laws and other barriers, couldn't be met by his then-current project.

"So I thought, 'Why not put together a message board and let these people talk to each other?'," Isserman says. The site currently hosts just over 665 communities, and expects to have over 1000 by winter -- each rare or orphan condition with its own resources and discussions.

Advice is a tricky business, and medical advice exponentially so. Isserman doesn't mean for RareShare to dispense medical information (the NIH does that very well, and the NIH Office of Rare Diseases and RareShare link extensively to each other) but to provide a focused community that can educate and point each other to resources -- an incredibly targeted about.com, if you will. Beta ends, Isserman says, when the site finishes building out community pages and starts building modules for tracking research papers, handling hosted info, and so forth.

Similar to the way about.com works, RareShare is seeking community experts to find and manage the flow of information on specific diseases. For instance, systemic capillary leak syndrome (a.k.a., Clarkson's disease) has been diagnosed in around 75 people since 1990, and involves one's capillaries leaking plasma into the rest of the body -- potentially a brutal limiter of lifespan. RareShare's expert suffers from the ailment and has been able to connect other sufferers to doctors on top of the problem. But he doesn't dispense medical advice, and those who would dispense medical device -- potentially a disastrous overstepping of the role of a good social network (or what a liability lawyer would call a good social network) -- are dealt with.

"We don't want pure medical info passed back and forth," says Isserman, and outlines a community-moderation plan that sifts relatively harmless tips about vitamins and homeopathic "treatments" from more serious material on wacky, ill-tested or plainly illegal medications or treatments. "As long as there's no harm," he says, "it's okay to post [tips]. If someone claims to have information on actual treatments or trials, we ask them to fill out a form and to link to the actual testing details, even if those are details on Phase 1 or Phase 2 testing. And we moderate." That said, Isserman allows that he'd be pleased to have representatives of the drug companies themselves dropping in to update communities on progress made toward treatments or cures.

Privacy's another issue for sites touching on sensitive medical data, and social networks walk a line between sharing and oversharing. "Patients are anonymous and users come first," says Isserman. That could present an interesting challenge down the road when the site seeks a revenue source that's not, as he says, "privately funded by me." But RareShare is "much more a social mission than anything else," he says -- and as with any other social network, success ultimately rides on building its audience even before clicking with sponsors or advertisers.