> if the example calls at I/O were not staged, and real calls, I suspect the recording of them would be illegal in many jurisdictions, including California.

Interesting implications there for how Google will measure / improve the effectiveness of Duplex. Where is the line drawn between recording a call and recording data derived from a call? e.g. clearly recording the call unilaterally is illegal. Presumably just storing a hash of the audio data would be legal, but also useless. Is there some middle ground that is legal, but also useful?