Talkative,
It is not that simple as you tried to make it. MrAlex has a valid point. And say one country wants you to kick your all attachments to other country (one in said dual) out from your heart and mind before granting citizenship, what will you do? Infact in many issues you do not have a choice.. Like you are a citizen of A and B countries and Country A make a law draft for compulsory enrollment in war against country B.. What will you do if you are a citizen of those both countries? And forget war, in day to day life Country A expolits country B economically... where and what will be your stand? If country A is more powerful economically then you will naturally favor country A (This is general human tendency..so do not take it personally) and in that case why on earth people/system of country B trust you and should still allow you to enjoy the citizenship of country B? I have fundamental question why on earth people should accept citizenship of country A if they are already citizen of country B unless they have faced political/social discrimination in any sense (And in that case person will become ONLY citizen of country A with hatered towards country B and thus there will be no debate for dual citizenship)and particularly just for short term economic gain? And again if they accept citizenship of any particular country for their economic gain then do not you think that this tendency will make them again immigrant if that particular country gets economically weak (Hypothetical scenerio)? And why on earth people of that country should assume and believe in the loyality of those new citizens ( immigrant becoming citizen just for his/her economic gain)? The people what JoeF described, yes, that lot indeed does not have choice ( we may need different thread for this kind of people.. As these people belong to a big social/cultural/identity mess)but what about MOST of the other people except people who politically/socially discriminated..