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top 10k 10k…100k 100k…1m 1m…∞
     reCAPTCHA 0.25% 0.34% 0.28% 0.20% sites
     Mollom 0.0027% 0.01% 0.02% 0.01% sites
     n/a 99.75% 99.65% 99.71% 99.79%