In the main how good and helpful any online community is... Is totally dependant on how it is managed by the moderation/Admin team..
A online support community based on providing support for a medical condition, needs different abututes to it's moderation/Admin team than that of a supporting the use of the lastest software...
A good community, will be quite well balanced, with debate opposing view points, along side a moderation/admin team, who can not only ensure that the normal bullying, unethical tactics, are kept off the forum, but also spot dangerous information being given, and removed off the forum out of harms way.. They need to be able to pick up valuernable members, who ask for advice and it obvious that the information being given, is totally unsuitable, unsafe and probable leading not only leading to protential suffering but in fact leading the member into dangerous situation/harm..
Online comminties are and will always be open to several valuernabilities,
Varication of information provided
Ability to create multi-user names, which can be used to unfairly under-pin a dabate or information
No control, how any individual will percieve or understand information given..
and several more..
But over all, for the right person then a comminity can be a very good source of information which can be benifcal to them..