does Alexa listen in apart from when the name is commanded?
You're not getting it. It needs to listen at all times so it recognizes when you issue the vocal keyword. How else would it know you said it? If i'm not listening to you, why I know if you tell me a keyword?
Once it detects the keyword, it records your voice snippet and sends it to Amazon to fetch a response. That voice snippet is likely stored and probably associated with your email, which could then be used to build a profile of your interests. That data is worth money.
Also I like how all of you are terrified about Amazon Echos, but ignore the copious amount of data that is collected from you with every text, voice call, and online activity. And who cares? Unless you live like a hermit, this is the price to pay in a modern society with all the conveniences.
Luckily, nobody gives a shit about your family discussions, the complaints about your spouse, or the minutiae of your life. At best, they simply want to gather some data on what you want to buy, so they can sell it to other companies.