Ask YC: Retaining the Authenticity of Government Data

The government is currently considering a major overhaul of its public data services, making a wide assortment of APIs available for developer use.

It's all being held up by a concern that there will be no way for end-users to be able to discern the real data from manipulated or made-up data.

Are you aware of any best-practices for avoiding this problem, but also allowing the data to be freely available?