Amy Senger says access to data is an important way to keep people involved in an online community:
Keeping community members tied to data is key – the more they have access to, the better; the more the can do what they want with it, the better.
Without a reason to keep coming back to an online community, people will drift away. Data is often that reason to return, because people need it. Conversation and interaction come after people find the data they need.