i take it what you meant by that was that the term ‘marriage’ would have no legal weight and that the state would make no effort to define or regulate it - that basically any private institution or individual (religious or secular) could make its own decision about how to use the word.

Yes. Actually, now that I think about it, I suspect that this would undermine the roots of traditional marriage a lot more effectively than same-sex marriage would. Because it would mean that if the neo-pagans wanted to perform group marriages, or the Church of the Subgenius wanted to unite this man and this pineapple in holy matrimony, they could do that. Hm. That's actually a pretty good argument against this idea as being appealing to the moderate majority...