Keep your number? I love this XKCD on this [0]. I live in a different state that where I got my phone number and when I moved I just kept the number so I didn't have to go through the dog and pony show of updating it everywhere.
Are phone numbers insecure? Sure, yes, absolutely. But too many companies have built their entire brand around not requiring registration, that is their USP (e.g. WhatsApp).
What Lyft should be doing at the absolute minimum is merging the phone number with the IMEI (or some other unique hardware ID) and only then allowing people to make purchases without re-entering the CC number.
It won't fix the problem of if your phone got stolen and someone made purchases with it. But it would stop phone number re-use related issues.
Well put. I can think of a half-dozen phone numbers I used to have that have presumably been reused. Though even email addresses can be reused: Yahoo announced in 2013 it was doing this.
From a HN app/service-development perspective, all of these approaches have tradeoffs. Facebook login gives you a scoped unique ID with a low probability of reuse (perhaps zero, I can't recall what the docs say), but some folks don't like logging in with FB or don't have a FB account at all.
My backup plan at this point is probably a 'quick' reimplementation of the bits of GV that I use in Twilio.
EDIT: As Someone1234 points out, however, caller-ID might be irrelevant, and having GV might not help. Another reason to be very selective about what apps you install.