Why Use Plone
Plone is among the top 2% of all open source projects worldwide. It has had over 89,000 commits made by close to 800 code contributors, representing close to 1,250,000 lines of code. This is the equivalent of an estimated 350 years of effort. Plone is supported by more than 350 solution providers in more than 100 countries. The project has been actively developed since 2002, is available in more than 40 languages, and has the best security track record of any major CMS.
Source: Open Hub, February 2015