I like America. I don't plan to leave but yes... many wealthy people already have secondary citizenship. Jim Rogers says you should think of it like insurance. Hopefully you don't need it but for a variety of reasons it's a good idea to have a backup plan.
Secondary citizenship is not the same thing as denouncing your citizenship and fleeing taxes. US citizens are taxed worldwide, irrespective of location or other citizenship status. Your point is taken, it's just not relevant.