No piece of technology knows as much about you as your smartphone. It goes where you do, so knows your movements, holds your contacts, your mesages, emails, web browsing records - and all the apps you use, perhaps including credit card details (suitably obfuscated to prevent casual theft). Given untrammelled access to someone's smartphone, you could find out almost everything about their life.
Smartphones are intensely personal (which is also why people can get so worked up if they think you're insulting their choice of smartphone; it's tantamount to insulting their personality). And when it comes to data, the events of the past six months - starting with the Guardian's revelations about NSA and GCHQ surveillance - have heightened peoples' awareness of the idea that it is their own data.
Smartphones are intensely personal (which is also why people can get so worked up if they think you're insulting their choice of smartphone; it's tantamount to insulting their personality). And when it comes to data, the events of the past six months - starting with the Guardian's revelations about NSA and GCHQ surveillance - have heightened peoples' awareness of the idea that it is their own data.