MDH, some good readings on geolibertarianism are at http://earthfreedom.net/ecolibertarianism. You are right that reversing the appropriation of ground rent seems to require local monopolies on governance. But in the absence of idealized initial conditions (i.e. covenants in force across entire regions), this is also true for dealing with public goods, common goods, and club goods. For one proposed governance model, see "the organization of government" in Fred Foldvary's model geolibertarian constitution: http://www.progress.org/2007/fold523.htm. I'm especially intrigued by demand-revelation voting on public goods, but I still have some questions about it before I can endorse it. As Foldvary always points out, geolibertarianism favors not central world government but radically decentral federated governance. The people you exclude from your land are your neighbors much more so than people on other continents. Also, most public services increase the value only of land within the radius of ordinary daily travel. Any public service serving a wider area can easily be handled by federation. Foldvary actually calls himself a geoanarchist, but his idealized private communities would have monopoly powers that to me make them indistinguishable from local geominarchist governments.
Paulie, returning geo-rent to the community would surely cause denser settlement for the vast majority of people who want proximity to urban amenities while minimizing their share of the cost (which would be assessed per unit area). Land-holders on less-dense parcels would in urban areas tend to be bid off their land (when land changes hands) by people wanting to develop more densely.
Woof, defenders of land value taxation include many of the most famous thinkers of the libertarian and classical-liberal tradition: http://earthfreedom.net/lvt-advocates.
"Intelligence, talent, and ability" never generate classical factor rent because they don't generate any return above the amount necessary to keep them in their most productive use. Beauty could arguably generate a classical factor rent because (like fame, athletic prowess, trendiness) it is a positional good -- one whose value depends on its ranking/exclusivity and thus is hard or impossible to substitute or expand in supply. (There can only be one Michael Jordan in a given era.) However, such personal attributes are very obviously the property of the person himself -- indeed, that's why "attribute" and "property" are synonyms. By contrast, there is nothing that naturally ties any geographic site to any particular person. Being able to cut off people's access to a part of Earth's surface doesn't make you king of it.
Tom Knapp, I too resisted Georgism as strenuously as I could when I was first exposed to it back in the 1990s. I especially resisted the idea of being bid off "your" land at a moment's notice, and nobody told me this can be replaced with a policy off collecting only realized geo-rent -- i.e., collected rent or sale proceeds that embody the future rent stream.
Steve Linnabary, I agree that the DoI captures the essence of Libertarianism -- Portland style. The DoI says that "to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, [and] that whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness." It was only in Portland that the LP Platform finally said "Government exists to protect the rights of every individual including life, liberty and property." And it was only in Denver that the Platform said "Whenever any form of government becomes destructive of individual liberty, it is the right of the people to alter or to abolish it, and to agree to such new governance as to them shall seem most likely to protect their liberty."