Like many things (social networking, digital AI assistants, keyboard text prediction) they are creepy because they are closed-off and proprietary and you have fuck all idea what's happening with your data, besides vaguely knowing you're being monitored in a way Orwell could only dream of.

Once you take out the fact that e.g. messages you write are being recorded, your speech is being monitored 24/7 by a microphone in your home, or all your text input is being stored in somebody's server halfway across the world, those technologies could have the potential to be really neat indeed.

One can dream.