There are many things in election systems I don't really understand. One such example is being able to vote while not living in your country of citizenship for a very long time.
NOTE: I am only using the US here as an example. The issue is likely present in many other nations.
I have a friend who moved his entire family to Australia twenty-five years ago. They have no intention to return to the US. They can, however, vote one every election. Of course, the reason is that they are US citizens and they our laws grant them this right. And yet, I think it would be just to consider that this should not be allowed.
Why?
If you have relocated to another nation and become a citizen of that nation, your vote is forcing a choice on those living where you used to while you do not have to live with your decisions.
Say you vote for a tax increase. Everyone pays. You don't. Say you vote for a serious change to laws pertaining to education. Everyone has to live with your decision, you don't. You vote for a lunatic for president, governor, minister, whatever. No consequence to you. Not the same for those still living there.
Perhaps the requirement should be that the person has to have lived in-country for a minimum of five contiguous years prior to casting a vote. That means you have been a part of the affected population recently enough and long enough to have "skin in the game".
There is another side to this idea which takes a very different path:
Voting as a weapon.
Imagine a scenario where a nation with billions of people under totalitarian regime sends millions of people to another nation. They instruct them to stay there long enough to become citizens of that nation. In the US that would be about two years. After that, they are forced to repatriate (perhaps there's an implied threat to their family, which ensures repatriation). Once back, these millions of people can be ordered to legally vote as citizens of the other nation. They would vote as directed by the adversarial government. This government could use remote voting as an economic tool and, in many ways, a weapon of war.
What happens if this adversarial government systematically plans and executes such a strategy over decades. At some point they could have control over tens of millions of votes in other nations through their planted naturalized citizens. They could, quite literally, sink entire economies into chaos.
Impossible?
Well, the laws, as far as I know, would not prevent such a scenario.
Either way, I sometimes feel that those who chose to leave a country behind and emigrate to other lands should not have to right to vote and influence life in the country they left.
EDIT: Wow. Really? Why are people arguing about US-specifics that are utterly irrelevant rather than discussing the concept of the potential nefarious use of "remote voting" in any nation? Didn't read my note at the very top?
Geez.