I guess you'd need some kind of captcha, otherwise everybody will put their old gpu's out mining spam and moderating the crap out of it.
That's easily avoided, a simple "strike" system will do. If you get too many peer moderated strikes, your account get banned for a period of time.
Also, I think "account" would be a valuable thing, basically you get more trust/privilege/moderation/post per day etc... if you have a long account age without being banned. One ban would set your account back a lot.
Basically, a newly generated account would be worthless, can't post until online for x hours, can't enter "hidden forums", can't moderate etc... People can set up advanced forums, that only "aged" and well behaved accounts could enter.