It is not stable in the least for millions of Americans, especially those who live in poverty (I'm not sure about the rest of the world). Phones are lost or stolen, phone numbers changed because of being harassed by debt collectors, ex-partners, current partners, etc. And if it isn't stable, it isn't convenient.
My phone number changes every 2-3 years whenever I switch to a new carrier for their acquisition offer. Why would I port my old number when 9/10 people who call me, I don't want to be calling me? And heck, I don't exactly live in poverty, even if my (student and scum landlord) debt is significantly more than my assets.
It is better in the US as generally all plays are country-wide but as a Canadian my number has changed many times.
- First number.
- Moved to a different city for Uni. Switched number so that people didn't have to pay long-distance to call.
- Moved back.
- Move to Europe for a job.
- Moved back.
I would never consider an identifier that is (loosely) tied to your location stable.
It is not stable in the least for millions of Americans, especially those who live in poverty (I'm not sure about the rest of the world). Phones are lost or stolen, phone numbers changed because of being harassed by debt collectors, ex-partners, current partners, etc. And if it isn't stable, it isn't convenient.