Dual Nationality

Should dual nationality be allowed? I merely ask the question.

There are pros and cons for the individual, but I'm thinking more about the states involved.

For a start, was Nazanine Zaghari-Ratcliffe's plight made worse by having dual nationality? 

Also, in the absence of any mutual extradition treaty, a fugitive from justice can find refuge in the other nation within which they have citizenship.

I gave up my Dutch nationality when my father had me naturalised British. The reason for this was he knew I wanted to go to sea, and I couldn't become master of the British registered vessel unless I had British nationality. As a consequence, my Dutch nationality lapsed when my Dutch passport ran out and the Dutch did not allow dual nationality. Even now it's difficult for me to reclaim my Dutch nationality without living there for a year.