In light of the newish policy on area51 sites that potentially leech users from the "big 3", this should be made explicit in the area51 FAQ. At the very least, some reference needs to be made to the 'moderation' of SX sites.
We're still trying to figure out how Area 51 should handle duplication and merging, but we've updated the FAQ to include Joel's 5 guidelines for when sites should be merged:
Should my idea be part of an existing site, or its own site?
In general, if a site makes sense as part of a bigger site, it's better to have one big site than a bunch of little niche sites. Site X should be subsumed by site Y if:
- Almost all X questions are on-topic for site Y
- If Y already exists, it already has a tag for X, and nobody is complaining
- You’re not creating such a big group that you don’t have enough experts to answer all possible questions
- There’s a high probability that users of site Y would enjoy seeing the occasional question about X
For more information, read the post Merging Season on the blog.