[Fnoord]

I don't. My use-case, where you have a SIP client and WLAN, allows for you to be disconnected, and only connect when you feel like it. It is akin to Invisible mode on ICQ; and that was perfect for people who wanted to lay low.

[beerandt]

But why go to the trouble of that at all if you only want to make outgoing calls, and without giving people you call a return number to reach you.

[Fnoord]

People need your return number for voicemail (if you decide to opt into that; personally, I don't), and to recognize who's calling them. I know enough people who don't accept a call from a "private number" or "unknown number".

I have my smartphone 24/7 on DND. I only feel/hear my vibration motor if I get a call. Sometimes, this causes me to miss phone calls, but in general it works well enough. It also makes me one of these people who isn't annoying in public transport or on yoga class.