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An alternative would be to only show unapproved nodes to logged-in users.
But aren't they a "legitimate" target market for the spammers?
The other thought that crossed my mind was a "spam" button in the Approval nodelet for anonymous posts.
Once clicked, the only place that post shows up is in the 'nodes to consider' list; where it can be restored with 'Keep' if the spam button has been abused.
The idea being to make the marking of spam a considerably simpler & quicker process than the current 4 present & cooperating monks + a downvote (== extended time when not many monks around).
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.