Terms: http://www.netatmo.com/en-US/site/terms#div_terms1
Privacy: http://www.netatmo.com/en-US/site/terms#div_privacy1
1. Can you control who has access to your data?
You grant Netatmo a “perpetual, irrevocable, non-exclusive, worldwide, royalty-free license” and “waive any rights of publicity and privacy”. Also, “with registration to the Netatmo Services you automatically Opt-in and allow us to share your Personal Data with third parties because you agree to be contacted by such third parties with respect to products, services and/or events that may be of interest to you.” :@
2. Can you export your data?
You can’t download all your data, but the data can be accessed through their API.
3. Can you close your account?
There is no obvious way to close an account. 
4. Can the terms change without prior notice?
“Netatmo reserves the right to update or modify this Privacy Policy at any time and from time to time without prior notice.”
5. Can I trust them to keep my data secure?
Netatmo’s website supports, but does not enforce using a secure connection (HTTPS).