This is certainly a subject needing more honest consideration politically. I favour a shift of taxes off incomes and consumption and onto land. However, something major has changed since Henry George’s time.
The efficiency of global transport systems, and freedom of trade, has rendered most resources “super abundant”, and competition between resource owners globally depresses real commodity prices to something a lot closer to “costs of extraction”. Back in the era of George and Marx, resource owners generally wielded a power of “monopoly” rent – they could charge whatever, ultimately, end consumers of products within relatively closed and relatively “local” economies could be gouged for.
The term “differential” rent has been coined in economic literature since the 19th century, to describe “rent” that is NOT “monopoly” in nature. A “differential” rent is what the owner of a resource can capture because of the advantage of his location relative to other sources of the same resource (ease of extraction of the resource matters too).
For example, the Arabs have lately been capturing “differential” rent for their oil, because they cannot sell it for more than the owners of the next-most-cheaply-extracted oil source (or even substitutes). A gouging scheme like OPEC of course would have put some proportion of “monopoly” rent back in – but even then, the rest of the world does not sit around not looking for alternatives.
But the nature of “resource rents” today means that it is not the same source of taxation revenue that it might have been once. Now, a national tax on “resource rent” may well result in global customers looking elsewhere in the world for the same resources. The fact that there is already a “Mining GFC” indicates that we are still in an age of superabundant resources and the chill winds of the free market.
The whole point of a “land tax” is that it incentivises the land owner to at least put the land to best use, not withhold it from the market anticipating more capital gains. Resources you dig out of the ground are quite different to this.

More:

http://www.macrobusiness.com.au/2016/03/could-a-137-year-old-equation-explain-financial-collapse/#comment-2568105

Phil of NZ;
An interesting thing happened on the way from Peak Oil.
Unexpectedly after the peak of crude oil in 2005 and the rise of
fracking and other expensive oil and the crash in 2008 in the following years demand declined and pushed down the price of oil to the ecent levels.
This was a completely unexpected effect of the high prices in 2010 to
2014. The resiliance.org web site has a number of articles about this
strange situation. Look for articles by Gail Tverburg.

The situation is that it is expected that 30% to 50% of US oil companies
will become bankrupt later this year or next year.
Bankruptcies have been increasing very significantly so far.
These are of course the heavily geared small tight shale fracking Companies.
The number of drilling rigs in operation has fallen since Jan 2015
to date from 1600 to about 464 this week. That speaks for itself.

If the decline rate exceeds the demand decline rate then the price
will rise. It is complicated because Iran & Iraq are expected to increase production.
Interesting times.