[akg]

Interesting idea to use optionally registered accounts for moderation; although I guess it kind of digresses from the point of anonymous posts.

Interesting idea to use mturk, it would probably be cost effective but the turn-around time may not make it feasible.

[prawn]

On one of my sites, a higher level of moderator has access to edit/delete while basic moderators (any regulars, basically) can "sin bin" a post for review/attention. Seems to work reasonably well in catching the worst posts.