Bruce Schneier writes:
… Being able to record the police is one of the best ways to ensure that the police are held accountable for their actions. Privacy has to be viewed in the context of relative power. For example, the government has a lot more power than the people. So privacy for the government increases their power and increases the power imbalance between government and the people; it decreases liberty. Forced openness in government — open government laws, Freedom of Information Act filings, the recording of police officers and other government officials, WikiLeaks — reduces the power imbalance between government and the people, and increases liberty.
Read more on Schneier on Security.