How much is akismet?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Micah Fisher-Kirshner: It's free for non-commercial use, but never looked at their ToS.
  
  My guess is it's free for non-commercial use in order to improve their data pool as only collecting data from paid customers would be too small to be useful to detect spam.
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  Ian Dixon: I hadnt thought of it as a way for them to get their research on what might be spam done for free +Micah Fisher-Kirshner ;so a very good point on their thinking
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  Lori Eldridge: I use Akismet on WordPress and the $5.00 per month is worth it's weight in Gold because it stops about 3,000 spam per month. I don't even need to deal with it as it handles it all.
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  Justin Y: It's good, it's free like +Micah Fisher-Kirshner mentioned but I don't think it's full proof.
  
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  Ian Dixon: Akismet is a computer program so it is far from foolproof and will produce false positives so agreed on that one +Justin Y ;
  However it is not free for most uses. To quote from their page
  'If your site is for a business or if it promotes a product or service, you should pick from one of our paid account options.'
  That means a minimum of $5/m per site for a low traffic level
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  Justin Y: +Ian Dixon yeh I know and five bucks here and 5 bucks there adds up real quick, which is why use other resources to protect my sites from spam.