Cross-site interfacing - architectural advice needed

[eluser]nZac[/eluser]
Well this is an interesting one. Let me ask a few clarifying questions.

1. Does each child site hold all of it's own products or does the parent site have a master DB?
2. The parent site authenticates the user on the child site?
3. Can child site access parents sites DB or are you running it as the parent servers the child the information?
4. Is it going to be AJAX ran?

Just some questions to clarify for me.

Cheers