Rob - Alan is referring to the highly-preferable-to-me situation in which "marriage" would simply be a collection of contractual rights/responsibilities between consenting parties.

The government would only get involved in the event of a dispute, and anarcho-libertarians even postulate systems in which a government need not be involved in such things either.

Again though, I think it is unreasonable to expect real people in the real world to wait for this paradise, and to hold off on recognizing their situation until we reach that anarcho-syndicalist holy land.