Terms: http://www.fitbit.com/terms
Privacy: http://www.fitbit.com/privacy
1. Can you control who has access to your data?
You grant Fitbit a “perpetual, irrevocable, non-exclusive, worldwide, royalty-free license” to your data. Fitbit can give “non-personally identifiable aggregated user data” to advertisers and other third parties.
2. Can you export your data?
Exporting data requires a paid plan, or using their API. 
3. Can you close your account?
Fitbit deletes all “personally identifiable information” when you close your account, but “may continue to utilize de-identified and anonymized historical data”.
4. Can the terms change without prior notice?
Fitbit states that it “may” communicate “significant” changes. :huh:
5. Can I trust them to keep my data secure?
Fitbit’s website supports, but does not enforce using a secure connection (HTTPS).