Having seen the videos for Horizon, i've got to say i'm a little disappointed - I don't think it's what i'm after so it's unlikely i'll use it - not a problem. Facebook laid out these observation and moderation tools in a “Horizon Safety Video” and explained them in further detail in an interview with Road to VR
First, all the users in Horizon
are involuntarily recording each other. The last few minutes of everything that users see and hear is recorded on a rolling basis. Facebook says this recording is stored on the headset itself, unless one user reports another, at which point the recording may be sent to Facebook to check for rule violations. The company says that the recording will be deleted once the report is concluded.
Second, anyone you interact with can invite an invisible observer from Facebook to come surveil you and your conversations in real-time to make sure you don’t break any rules. The company says this can happen when one user reports another or when other “signals” are detected, such as several players blocking or muting each other in quick succession. Users will not be notified when they’re being watched.
And third, everything you say, do, and build in Horizon is subject to Facebook's Community Standards. So while in a public space you’re free to talk about anything you want, in Horizon there a many perfectly legal topics that you can’t discuss without fear of punitive action being taken against your account.