The technique that works best against professional spammers is opacity and unpredictability in detail. If they don't know what's happening to their spam, if they don't even know when they can expect to suspect it was spotted, if they don't pin us down up front about EXACTLY what percent of a site is outside advertising, then they don't know how to manipulate us next time around. If they don't know EXACTLY how many words of verbiage, how many millibits of actual information, then they can't reliably fire off one site and start loading the next round of their fifty-seven flavors of doorway spam. If even the technique of aiming to supply the second-worst site in the category results in a failure, then what's a poor spammer to do?
Eventually (and this will take a long time, because many of these weren't the brightest glowworms in the swamp to begin with, many are of the travelling-salesman mentality, congenitally disposed to regard persistence and luck and plausibility to an idiot higher than skill and knowledge and reputation anyway, and many are financially driven to desperation beyond the bounds of sanity) the word sinks in.
Spamming doesn't pay. Submit like you were intending to follow the rules, or don't submit at all. The ODP is dead: dead to your persuasions, your blandishments, your deceptions, your peremptory demands, your self-centered priorities, your greedy desires, your fatuous attempts at manipulation.
Meanwhile, the people that are trying to help (webmasters whose real purpose is building their website SINGULAR, not targeting the ODP for listings PLURAL) just go on about their business, building their site richer as their knowledge and experience grows, confident that sooner or later people will notice sites that reflect personal authoritative knowledge.