[thelist] co-branding architecture

Hello

Did anyone work on cobranded sites? I need all the info i can get about the general architecture for cobranded sites. For example:

Whats the best server/application architecure to use?
How do cobranded sites like below function:

(where are they should be hosted (ebays site/ partners site, how does maintenance work, I presume changes on the main site update all the partners), 

www.ebay.com
http://ebay.icq.com/
http://ebay.go.com/


or here is another example:
http://www.varsitybooks.com/scholarships/default.asp?icq=true

Thanks..I appreciate your help

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