Most probabaly in US.
Based on project and money spent.

It depends mostly on the budget for the project. In a 
perfect world, the business analyst would want to get 
information first-hand, going to where the action is. This 
will provide more control over the project. However, if the 
project has budget constraints, the BA will have to resort 
to other ways of getting the job done: i.e. internet 
meetings, phone conferences, faxed reports, email, etc.

If the client from US then mostof the Business Analyst's  
resides in US and play as a on-shore team member. who 
interact with the client and team members
(DEVS/TESTERS/MGRS) for the particular project through 
emails/ ON CALL to review and meet the client requirements.