[mlindner]

That's pretty interesting. I've had a twitter account that has no phone number and no email for a very long time. It's never been blocked.

[Avamander]

If you've had the account for very long it's probably grandfathered.

[mikemac]

Be careful, my 10 year old account was permanently suspended without warning and support is no help; I suspect it's because I didn't have a phone number on my profile.