Taxing global income - not a good idea wholly

I havent seen the details of the proposal, but if what I have heard is true, then, the Obama administration is going to tax all global income for corporatiosn. I can understand and agree with the rationale for dealing with companies who use tax havens. But I cant accept the logic for taxing in the US, the income say a company like CISCO receives in India, if the CISCO is already paying taxes in India. Where is the incentive to go overseas then?