I have thought about this before as well. I think there is a benefit to a thread on OSI, as I've encountered more than a few troops who don't know where to turn for help, or what resources are out there. But I believe it would need to be well mentored to prevent it from getting off the rails.
There is also an inherent risk of of a person's information being misused or abused, or for them to be taken advantage of. Another concern I have based on some other online sites I've seen, is that they foster a very dangerous negativity towards the health care system, towards accepted and proven medications and treatments, and towards the chain of command. For example, I've seen instances where a very vocal person has slammed a clinic, labelled the help as worse than useless, and the system as out to get them, all because they didn't get medicinal pot. Others chime in about how terrible that is, and how this drug, or that alternative treatment is the best thing going, but it isn't approved. How does that help a young soldier looking for treatment?
As Vern noted, there's more than a few very helpful people on this site. They will do anything possible to get a member linked in to the care they need, or simply to be there for support.
As for myself, I was given a diagnosis of moderate to severe PTSD a couple of years ago. I am part of the Health Services, and I work at Director Casualty Support Management/Joint Personnel Support Unit. So, I'm not just a Staff Weenie, I'm also a customer. I will always do whatever I can to provide assistance, advice, or a friendly ear to listen to anybody impacted by an Operational Stress Injury. I may not have the answer at the moment, but I'm certainly linked in to the proper resources, and can find answers and hopefully help for the member quickly.