Reading Usable Help
@UsableHelp on Twitter
Gordon R. Meyer
Allowing readers to supplement your documentation with comments or additions is an appealing prospect, as discussed in An Example of User-Supplemented Help, but it also opens the door to off topic, if not inane or offensive, additions that might escape immediate notice.
In Internet Comments as Heckling you'll find a reasoned argument about how website comments seem to bring out the worst in people, with concrete examples that will be familiar in tone to most anyone.
Dealing with these issues will need to be a first priority for any documentation system that allows others to add their unfettered perspective.