Security
There are various dangers involved in participation in on-line forums. Pro-choice forums have additional dangers.
Intervention
An obvious danger which is unique to ash-related forums, is intervention. That due to suicidal thoughts you might be hospitalized, or have other action taken against you. The main thing you can do about it is to remain anonymous by using throw-away email accounts.
Cyberstalking
There have been reports on Cyberstalking on ash-related forums. A specific account appears in the ash archives.
Impersonation
Perhaps less dangerous are people who invent stories in order to get attention. Here is one account.