While I would understand refusal to do so from non-technical crowd (e.g /r/technology or similar cesspolls), it's very difficult for me to understand this argument on hackernews.

I obviously agree with you as the GGP, but the logical counterargument would be, these phones upload so much data in the normal case that it's hard to know what's what. And all of it is encrypted with https, often with certificate pinning.

But, well, audio files are really quite large, at least in the quantities we're discussing. And so in order for the data transfer to go unnoticed, the phone would have to be processing it locally, to decide what to upload. That would be a lot of work, in terms of cpu usage and battery life, and that, again, should have caught some researcher's attention.

Suffice to say, while I don't think any of this is feasible today, this is why locked-down devices and certificate pinning scare me. Audio is expensive, but you can learn a lot with a keylogger.

PRISM was operating at the network level, as opposed to widely-available consumer devices. It's the difference between tapping a phone line at the call center, and going into every individual person's house and planting a bug under their counter.