Allowing that sort of sentence construct violates the privacy afforded by starting with the key phrase. If the Echo did allow this, I would not own one since it would send a lot more unintended sentence fragments to Amazon.

By saying "Alexa" first, it gives me a chance to hear the wake-up tone before I continue my sentence.

So if I'm saying to my friend Alex "Alex uuh, tomorrow we will rob the bank", I have a chance to stop before incriminating myself. But if I say "Tomorrow we'll rob the bank Alex uh... are you in?" and the Echo interprets that as a command, then it's too late, it's already been sent and analyzed.

It's strange that you'd have concerns about privacy when it comes to sentence structure and not that you have a literal black box with a powerful computer and an always on internet connected microphone in it.

Are you talking about my phone, my car, or my TV?

I trust Amazon more than Samsung, Chevy or, well, Samsung. But at least I can verify that my Echo is not sending home unusual amounts of data when it's not in use.

Isn't it really easy to run your own code on it? Not really a black box. Except well, literally.