The thing you're missing is volume. Even if you assume the vast majority of people will attempt to mess up your data, when you have enough people doing it, you can look at them on aggregate and based on patterns disregard bad data. It might be "expensive", but still worth it.
The thing you're missing is volume. Even if you assume the vast majority of people will attempt to mess up your data, when you have enough people doing it, you can look at them on aggregate and based on patterns disregard bad data. It might be "expensive", but still worth it.