[davidkellis]

I've been bitten by this before as a customer. I tried signing up for FastMail and was unable to create an account because their signup page required I supply a non-voip phone number. My phone carrier - Republic Wireless - is a voip-only carrier. Google Voice is also voip-only. At least, that's how their phone number check reported my phone numbers.

[slivanes]

Unfortunately those carriers are also heavily used by fraudsters.

[techsupporter]

Which is hilarious because fraudsters can trivially acquire many "legitimate" mobile phone numbers by acquiring prepaid phones and there are entire forums (two on Reddit I know of off the top of my head) where people make a few pennies receiving and then sending the verification codes back to the scammer. I actually do a variant of this and keep a couple of crappy Android phones activated on two Sprint MVNOs that I can use as "throwaway" numbers for a service that demands a "real" mobile number for SMS. I have zero desire to give my actual mobile phone number to anyone except friends and family.

Meanwhile, people who are simply trying to get flexible--or, in the case of someone using a Google Voice number on a Google account with 2FA and a strong password, a more secure phone number than T-Mobile could provide--communications are needlessly punished.

[dylz]

Google Fi is not heavily used by fraudsters, but can't be differentiated against GV.