Thats a "It depends" question.
Scenario 1 you have all your hosting clients local... and need servers local so they can utilize maximum speed with good ping times. You may also have a nice setup with access to that datacenter so y ou would want all your servers in one place.
Scenario 2 you are wanting good worldwide coverage and want your servers all mirrored at different locations just incase one goes down. You would want to have servers in a wide variety of places to better suite your demand for international hosting.
I personally have 2 servers each at 2 datacenters... Texas and New Jersey.
I want one in London... or close to it. It just cant be in ireland, because irish stink (::cough:: John :: cough:::

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