[capsule_toy]

I wouldn't rely on this. My LINE was set to a prepaid number that I had let expire on purpose. I thought I would be fine because I also had a username set. When someone else registered my number, I lost about 90% of my contacts. The only contacts I had left were ones that I was actively in conversation with. I believe this was actually a bug, but there isn't much recourse if it happens to you.

[unsignedint]

Ah, I see... I know when they've started expanding outside of Japan, they've actually dropped requirements to have a phone number associated with the account, and allowed Facebook account and E-mail address in lieu. Although, the requirement has been in place for Japanese users for a while -- I think it's now universally the same.