Many people worked with him, he was willing to challenge the status quo and that means a lot of people wanted to be around him - he was one of the earliest scientists to sign up to help Science 2.0 after this first component launched. I don't know how he heard of us, he was just in tune with the broad science community that way.
Everything is numerical here - it makes it possible for people to change their profile names, their column names, article titles, etc. without breaking links. JC's official user number was 62 - but really he was number 3, when you take out me and developers and people who just signed up but weren't researchers and just wanted to comment without captcha - and the 2 before him were people I recruited. His column name was Chemistry Wide Open because that is how he lived science, and he wrote about whatever struck him, just like we all do.
I came up with Science 2.0 and a framework for what the future of science might look like regarding communication and publication and collaboration and participation, but those were really just clever buzzwords at the time. Jean-Claude was living it and he gave me guidance on how to make a difference without making a lot of enemies among the status quo. At a time when everyone in academia was paranoid about someone else stealing their work, JC opened his notebook to the world - you couldn't steal from him, he was giving his thoughts away to all of us. Starting in 2005, UsefulChem championed his Open Notebook Science. His bio page there still proudly displays his featured author status on our site.
So, for most people who will see our logo today and wonder, 'Who is that guy?' well, you never heard of him because he was always off helping science. Once he helped put Science 2.0 on the map, he did numerous other things for people in science and science itself.
Other people will write better eulogies - you can start with Antony Williams, creator of that Science 2.0 favorite, ChemSpider. I'll just say thanks...and GodSpeed to that big experiment in the sky.