The benefit of Multiple Business Groups over Single Business Group

Hello,

I am wondering if someone could provide a summarized list of advantages to having multiple business groups in our HR setups. 

Currently, we have one primary business group and then a large number of HR Organizations.  These Organizations are arranged in Organization Hierarchies, and we use Security Profile's Organization Security to segment our data.  E.g. we have the following, and responsibilities such as 'ABC US HR Manager' tied to the 'ABC US' organization and below, and 'ABC Europe HR Manager' tied to the 'ABC Europe' organization and below.

ABC Co

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ABC US                                                                                                ABC Europe

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ABC US - HR       ABC US - Finance      ABC US - Sales             ABC Europe - HR           ABC Europe - Sales