An Amazon spokesperson gave Engadget the following statement on the matter:
"Amazon will not release customer information without a valid and binding legal demand properly served on us. Amazon objects to overbroad or otherwise inappropriate demands as a matter of course."
Echo only captures audio and streams it to the cloud when the device hears the wake word "Alexa."
Those clips, or "utterances" as the company calls them, are stored in the cloud until a customer deletes them either individually or all at once.