To expand on Anton's answer:
Jeff Atwood commented on the StackOverflow blog
We generally wait 4-6 months until a site has enough data to be useful.
referring to the cc data dumps that already exist for StackOverflow/ServerFault/SuperUser.
As I understand it, the Data Explorer tool Anton mentioned is based on these database dumps. It doesn't pull anything from the live StackOverflow database.
See this question on meta.so.
