My vague recollection is Apple would actually take the Siri request and route it to Bing for you, so Bing doesn't know your IP, and they would attach a unique i

My vague recollection is Apple would actually take the Siri request and route it to Bing for you, so Bing doesn't know your IP, and they would attach a unique identifier that they'd rotate every 15-or-so minutes, so that way Bing can correlate multiple requests done back-to-back but loses any correlation with requests outside that 15-minute window.