With Spam Karma there are things that can be detected such as:-

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document.write(”);

(end of code)

Here are my 6 months stats

* Total Spam Caught: 19214 (average karma: -11794.48)
* Total Comments Approved: 1447 (average karma: 11.48)
* Total Comments Moderated: 567
* Current Version: 2.3 rc1

I have seen an increase this month, up to currently 300 spam per day, but that is a fraction of what other bloggers receive.

Almost all of that spam is using BBCode for the links.

There is another factor – eyeballs

If you are using Akismet, every once in a while you will go checking for false positives.

With Spam Karma I get emails for potential false positives and thus the amount of eyeballs on spam are greatly reduced.