A merged FF program would, in general, be a good thing. I wonder though if all the 'external partnerships' would be lost as a result. It strikes me that if the alliance airlines merge FF programs then that would need to be on a (more or less) exclusive basis. I find it hard to see the attraction to oneworld of thousands of Americans accruing miles on US to be able to redeem them all over the globe on OW. The only realistic case I can see for external FF partnerships would be in regions not well served by the alliance, which therefore demonstrates an intrinsic weakness in the alliance.