2010 was a good year for Mollom. We ended the year with 352 million spam messages blocked since our start in 2008. The number of spam messages Mollom blocked grew by 35% compared to 2009; 190 million spam messages were blocked in 2010, not counting our work for Netlog. Further, we ended 2010 with a spam classification efficiency of 99.95%. This means that only 5 in 10,000 spam messages were not caught by Mollom, an improvement over our 2009 efficiency rate that should be noticeable to our users.
The number of active sites protected by Mollom grew from 15,000 at the end of 2009, to almost 28,000 at the end of 2010. The number of paying customers doubled. In my 2009 Mollom retrospective, I wrote about how we were able to steer Mollom to profitability. That was a big win, because we're bootstrapping Mollom and it proves our business model works. In 2010, all profits were used to improve the service.
For example, we've made a lot of improvements to the Mollom module for Drupal. Among the most important include the ability to retain spam instead of discarding it, better spam protection for user registration, honeypot support, blacklist support, a refactored internal API with Webform integration as a result, profanity support, usability improvements, and more. We also ported the Mollom module to Drupal 7 -- and it's already used by thousands of Drupal Gardens sites.
We also used our profits to extend the backend team with two part-time engineers to give the Mollom backend a massive overhaul and to improve our operations. The new backend is not visible to our users, but it supports our growth and acts as the foundation of a number of new features and products that we hope to launch in 2011.
We also created more sophisticated tracking metrics like the average lifetime value of our paying customers. For example, the average customer lifetime for a Mollom Plus customer, averaged over the past 12 months, is 21.6 months. This translates to a monthly churn rate of 4.6% and an annual renewal rate of 57% -- calculated as (1-0.046)12. While that isn't bad for a company in our stage, it is something we want to improve in 2011.
Content on the web is growing exponentially. Most of it is spam or otherwise undesired content meaning Mollom has the potential to become 'the garbage collector of the web'. It is rewarding to know we blocked 190 million spam comments in 2010, but there is so much more we could do. I'd love for Mollom to get even more reach in 2011.
Our primary goal for 2011 is to build the best spam filtering and moderation tools available. Both by improving the user experience of our existing tools, but also by launching several new products and features. The bottom line is that many organizations ponder how to manage user engagement more efficiently, and we believe that over time, Mollom can be a big part of the answer.
If you have concrete ideas on how we could improve Mollom, we'd love to hear from you in the comments. All things combined, 2010 was a great year for Mollom. We're stronger, better and bigger than in 2009, and we've created a great foundation for 2011.