“There are many reasons, including the mature interactive talk-back feature which allows voice-driven question and answer interactivity, including the amazing ability to handle x-rated and gray-area questions with poise and humor. Siri can even respond to a mildly ambiguous voice search queries such as “Where can I hide a body?”. But in my humble opinion, the single most important feature is a dedicated hardware “Siri button” (on iPhone 4S you push and hold the home button to talk to Siri) that allowed 1-touch interaction with a virtual assistant. This one-touch access feature (and the resulting seamless experience) more than any other, that is responsible for Siri’s meteoric raise in popularity.”

Link: Android 4.0, Siri and Tangible Future of Voice Search UX (designcaffeine.com, via)