I had Microsoft do this. They notified me that my account was being suspicious, so I needed to provide a phone number to use it. I had literally just made the account though, zero activity at all. It was just to force me to give a phone number to them for their data harvest

I ran into this with MS as well. However, they explicitly stated that it did not need to be my phone number. So since it was for a work thing, I ask to use my boss' number to get around the lockout. Seemed pretty pointless.

One of my land-line numbers is so spam filled, i ignore it and use it as the default phone number for such antics.

I disconnected the ringer so it doesn't bother me.

Welp, it's a good thing these companies don't have a large amount of control over a lot of people's lives. And luckily their business practices are transparent and we all agree they're fair.

This is fine.

So basically if the phone companies lowered the price of buying number lists then a bunch of web2.0 companies' valuations would evaporate?

Hey, I have some experience creating intentionally suspicious Twitter accounts.

There is no phone number requirement. They're just as happy with an email address.

If you provide neither of those, then your account functionality is restricted (with a big obvious banner showing at the top of every page), but you still don't get blocked.

Once I needed to create several accounts at once and then have all but one of them follow the last one. Those accounts got blocked, but it's hard to blame Twitter for that.