As far as I understand it, if I'm wasting a bunch of land and refuse to sell it, but there's a million acres next door that you can buy for pennies and your project will work just as well there as it would on my land, there's no case for eminent domain. Go buy that other land and build there.
Eminent domain is for stuff like, we're building a highway from here to there, and the only reasonable route is through there, and that's where your property sits, so we'll take it from you even if you don't want to sell, because this highway will have a big public benefit that outweighs your personal property rights. If the highway can just move half a mile to the left to the land of someone who wants to sell, then you do that instead.
On the internet, all property is adjacent and nothing has to be in a particular spot. The supply of domain names is effectively infinite. I don't see the case for taking one just because the owner is "wasting" it. You don't need that specific domain, just buy the one "next door", which on the internet is all of them.