>If you get a spam call / text, you can block that number from calling / texting you again.

>I can already do that on my phone, and it is kind of useless due to caller-id spoofing that most robocallers use.

Yes, I cannot see in which way this "black-listing" on Mozilla is different/better.

> Also, probably wont work for services that require a phone number but don't accept VOIP numbers.

I'm running into an increasing number of these, and it's annoying because I use Google Voice as my primary phone number. Using VOIP is important for me because I travel frequently between the US and EU.

Aside from being inconvenient for me, I take blocking VOIP as a red flag that the service might want to misuse my phone number.