They are moving people from low population servers to MEDIUM population servers. So it wouldn't bring problems to high population servers.
And why would it be a problem if low population serrvers become a ghost town? is there anyone right in his mind that would really stay there? They'll soon notice that their server is gonna be abandoned and move themselves. It's not like it costs them something to do it.

On the other hand, moving people from medium pop server to low, wouldn't work. Who would abandon a place that's actually fun because he sees people around, to try his luck in a server with much less people?

Mythic should be definately applauded for offering this kind of option so promptly.