I think it's safe to assume that the majority of users are good actors. With that in mind, the two main attacks that these sorts of crowdsourcing apps need to f

I think it's safe to assume that the majority of users are good actors. With that in mind, the two main attacks that these sorts of crowdsourcing apps need to figure counterattacks for are: 1. Minimizing the damage an individual can do. This is usually pretty easy to solve. InStock has the issue that a unique item could be said to be out of stock, and not have any other users report otherwise for a while. 2. Minimizing the damage that a coordinated group effort can do. This can be difficult to solve. The attackers will likely succeed for a while; you'd need a system in place to detect anomalies (or at worst, rely on users to report the issue) and a weighted scoring system (20 brand new users shouldn't sway what an active 6 month account says, etc). I've yet to see TP come back in stock at my local grocer during my trips, so I hope this project succeeds.