Ну ладно, напишу. Выродю что-нибудь :)))
1. People immigrate due to many reasons: political reasons, education, financial reasons, when they get married, etc.
2. Usually people immigrate to rich and developed countries, so on one hand it's better for them. On the other hand, it's bad because they often miss their home country.
3. a) It's bad for a country when its best citizens immigrate and represent another country. It's called 'brain drain'. Actually, it's a shame for a country when its best people don't want to live and work in it.
b) But it's not so bad when they live and work in other countries being the citizens of their own country.
4. a) Sometimes people envy them, sometimes people see them as traitors, but mostly they miss them in their own country or they just don't care.
b) When people immigrate in great numbers from developing countries with unusual traditions to developed countries, they may be accepted with hostility in their new place of living. When people immigrate to very large countries that have lots of immigrants, they are usually accepted well.