As a user of a product or service you want to maintain a certain kind of status quo for what you expect the product usage to be like and what sort of interaction you're going to have with it. This status quo is a sort of "goldilocks"-zone where you want to keep your users secure and trusting of your product. But what happens when you let your users make the content that other users can see?
The Trust Fence.
At HotSpot we recently allowed businesses to engage with our users directly in a system we engineered to be mutually beneficial to both. Businesses can show short and concise ads to users if they agree to pay for some increment of their parking. It's a system that lets businesses show ads to potential customers already downtown and gives the user of our platform something in exchange for that brief moment of their attention.
One of the big concerns with this for me was to ensure that businesses wouldn't create annoying (or worse, offensive) ads that would enter the ecosystem without monitoring. To prevent that, we decided it would be better to delay the actual start of ad campaigns until someone at HotSpot was able to review it.
In our case we were more willing to ensure that every ad was checked before letting it go live for our users to see. In the future, we could expand our "trust fence" by letting clients who have already followed the business to see their ads before approval is granted, or by letting trusted advertisers have a quicker process.
Keeping the user's interaction with your app stable and predictable might seem boring, but it will actually build trust.
The Awkward Filter.
Likewise, there are some downtown businesses that won't show up as near you when you park with HotSpot in Fredericton (no bonus points for guessing which aren't listed). This goes in line with the same as above, keeping the status quo of what the user expects.
In the past I've had Amazon and StumbleUpon both email me with automated and horribly mistargeting (and, some might consider offensive) suggestions. Our solution at HotSpot so far has been to avoid having potential objectionable content in our system to begin with, prevent the subjection of a user to one of those awkward moments.