On the final day of the first Plone Conference in New Orleans, a group picture was assembled. I think about 2/3 of the people there were in this picture. There's probably 3 or 4 times as many Plone developers and users in Europe than in North America, where this conference was held.

The last Python conference attracted about 300 people, or so I heard. It doesn't take much to realize that Plone is a leading force in the adoption of Python and Zope. It's a killer app on top one of Python's killer apps, Zope.