We already have plenty of secular communities. Hacker News, sports fans, standup comedians, book clubs, students in college, nerdfighters, groups organizing around hobbies and interests, groups of friends. Community forms not because religion has something sepcial about it, but because people tend to form communities around any subject they are interested in. Just because religion used to be there, doesn't mean we ha…
I think physical proximity is an absolute requirement for a community. Students in college inevitably form communities. They come together to help each other. Online forums like reddit more often drive people apart than join people together.