Ahh ... I think I see what you are proposing. No "free" e-mail addy can be used to register. No hotmail, hotpop, yahoo, gmail, etc. e-mail addy's are acceptable.
Yes, that would narrow the field. Only people who have an account with an ISP could register.
Also, it stops multiple account creation.
And would stop the husband/wife tag-teams here too ;-) Just kidding.
For a reviled public forum, FR has an amazingly small number of hit and run attacks.
Yes, the restriction on email account acceptance may have to be the first step. That's the rule over at the DUmp, and it's what keeps me from going over there and posting anything. I don't want anyone over there to be able to come back at me. Maybe it's time for that here at FR, unfortunately.