Todd Small was stuck in quicksand again. His brain was sending an electrical pulse saying walk," but as the signal streaked from his cerebellum and down his spinal cord, it snagged on scar tissue where the myelin layer insulating his nerve fibers had broken down. The message wasn't getting to his hip flexors or his hamstrings or his left foot. That connection had been severed by his multiple sclerosis. And once again, Small was left with the feeling that, as he described it, "I'm up to my waist in quicksand." Small would have continued just as he was had he not logged on last June to a Web site called PatientsLikeMe. He expected the sort of online community he'd tried and abandoned several times before - one abundant in sympathy and stories but thin on practical information. But he found something altogether different: data. There are a little more than 7,000 Todd Smalls at PatientsLikeMe, congregating around diseases like Parkinson's, multiple sclerosis (M.S.) and AIDS, all of them contributing their experiences and tweaking their treatments. The members of PatientsLikeMe don't just share their experiences anecdotally; they quantify them, breaking down their symptoms and treatments into hard data. They note what hurts, where and for how long. They list their drugs and dosages and score how well they alleviate their symptoms. All this gets compiled over time, aggregated and crunched into tidy bar graphs and progress curves by the software behind the site. And it's all open for comparison and analysis. By telling so much, the members of PatientsLikeMe are creating a rich database of disease treatment and patient experience.