like folks whose books get reviewed here

This is an important point, we should be welcoming to people we talk about, and I'm not sure how that fits in to any scheme. Send out preemptive invitations when we talk about people? Who would keep on top of that?

I wouldn't mind associating my website with my account - I already do, now that that's an available field. But even fewer people have websites than phones.

Well, that was the result of me trying to find a mechanism that wouldn't exclude you. But if we let people associate their account with a phone or a website, we include more people. It would be better to have more options to be more inclusive, if we can think of more specific options.

Wouldn't some kind of IP address thing suffice to rule out casually created socks?

Yes, for certain values of casual. You can hide your IP address by going through proxies.