You can trivially structure such a tax in such a way that going through a "forced sale" is going to be very lucrative (edit: elaborated in a sibling comment: https://news.ycombinator.com/item?id=37909570).
> It also defeats the object of land ownership[...]
So no, most people could keep land they'd like to keep in practice.
The entire notion of any sort of property tax is also predicated on the idea that individual land ownership is a tradeoff between the interest of the individual and society at large.
> The entire notion of any sort of property tax is also predicated on the idea that individual land ownership is a tradeoff between the interest of the individual and society at large.
Indeed, and I like this concept, I don't think we should ever "own" land in the same way as I own, say, my phone. All we ever do is borrow it from society (or even nature).
However, some aspects of land ownership are a net positive for society at large. In particular, the incentive to look after it better if it's really yours until you sell it or you die. With this in mind I like some proposals I've heard whereby unpaid land value tax can be accrued to be paid at death or on sale. That way the stewardship aspect of ownership is reinforced without the freeloading on land value increases.
Returning to the valuation question. I think you're assuming an efficient market when it clearly isn't one. It would be like having to reapply for your own job, except it's rebidding for your own house. Not a kind thing to do to anyone.
> It also defeats the object of land ownership[...]
So no, most people could keep land they'd like to keep in practice.
The entire notion of any sort of property tax is also predicated on the idea that individual land ownership is a tradeoff between the interest of the individual and society at large.