The subscription not being optional ("We don't make the subscription optional at this time", https://news.ycombinator.com/item?id=28351035), with unspecified consequences of not having one.
One thing I definitely gather from that comment is that E-Mails wouldn't work, which appears to be the main selling point of the device.
One thing I definitely gather from that comment is that E-Mails wouldn't work, which appears to be the main selling point of the device.