It might help, but it's a bit tricky, because there are virtual numbers (Google Voice), and banning those catches real users who use GVoice (like me). It's a tricky balance, and my sense is that like DRM, it usually ends up hurting legitimate users more than bad ones who will just use one of their many workarounds.

One thing we've had good success with in the past, but just couldn't afford once they raised their prices, was Sift Science. We've been meaning to try some of the alternatives to that.

Zumper also has some interesting ideas about it that they've used successfully in the past, that we're planning on integrating.

Having the time to do this (and not focusing on dealmaking) will be really nice :-)

I don't think it would. I messed with this scammer for a good while and I found that they either use Google Voice or apps like Burner to get new, virtual cell phone numbers easily.