I don't truly own my phone number. I barely control it. I can move it from provider to provider, kind of, but it's still not _my_ number – the number is a side effect of having cell service. In particular, if I move to a new country, what happens to my phone number? (Having recently done so, I still don't know: for now, I'm paying two cellphone bills, but that's obviously not a long-term solution, and I don't know what is. Port it to Twilio, I guess.)

You can make the argument that I don't truly “owns” the domain name off of which my e-mail address hangs, either, but it's a much better situation than phone number ownership. There, at least, the constraints of ownership (rental) are clearly defined, as is my ability to move it between registrars.