I recently read Liberal Archipelago by Chandran Kukathas. It is the best academic defense of exit as a moral principle, articulating a vision of society as a large number of sub-societies where people have the choice of which sub-society to join. I highly recommend it to to anyone interested in exit.
Kukathas bases his argument on freedom of association, choosing to jettison the traditional liberal focus on justice as the foundational principle of society. He bases his defense of freedom of association on the fact that different groups of people tend to have different conceptions of justice. The way to ensure these groups can live together without conflict, is to allow them to live under their different moral institutions, so long as individuals in such groups are free to leave and join other groups as they wish.
One implication of his views is the possibility of the proliferation of “illiberal” societies, such as the Amish, or more ugly, ethnic nationalist groups. However, under Kukathas’ conception, such a meta-society would be liberal so long as individuals were free to leave their group.
On interesting thing to note is his preface. He was influenced by libertarians, thanking both IHS and Liberty Fund, as well as a number of libertarian scholars. He also acknowledges the influence of both Hayek and Oakeshott on his work. That being said, Liberal Archipelago is squarely in the liberal tradition, with his libertarian influences having a much more subtle influence on his thoughts.