This feels like an "you're either with us or you're against us, Amazon B A D"-article.
The central thesis is misleading and wrong because it's NOT "unlimited, direct sharing of your WiFi to whatever Amazon users happen to fall and scrape their knees outside your home because they can't skateboard," it's "likely low-rate connectivity for other Amazon users' devices over Bluetooth or (maybe) Zigbee gated through Echo devices acting as bridges that happen to use WiFi as a backhaul."
Tile does the same thing already with their mobile app over Bluetooth - everyone with the app and BT on participates as a missing tag locator; Amazon is adding Tile into the mix (900 MHz BLE for Tile Pro) for another way to find tags.
Is Amazon going to suddenly allow or support BitTorrent-to-eSATA light dimmers (or some sort of WiFi backdoor)? IDTS. Where's the problem (other than opt-in vs. opt-out)?
PS: I worked in a radio group of a GPS manufacturer at the time when radio modules were in their kindergarten years. 900 MHz of BLE is always going to work better than 2.4 GHz for low rate data because of physics. 900 MHz is awesome.