Companion Marriage:

Prince Charles' marriage to be perfectly illustrates the case that given what marriage has presently become in Western Culture, there is no logical or fair reason for denying it to same-sex couples.

Their future marriage will have nothing to do with:

1) procreation (given their ages);

2) supporting or raising dependent children (given their children's ages and independent wealth);

3) supporting dependent (traditionally understood to be "female") spouses (given each spouses' independent wealth).

So why do they need to marry exactly? Even the sexual aspect -- I'm sure he's been boinking her for years (as I understand, he did this all throughout his marriage to Diana); it's not as though he needs to marry her to get "permission" to do that.

Their marriage will be about solemnizing companionate partnering and attempting to give a little bit of dignity to a relationship that is a fact of reality, whether we agree with it or not (and look at how many folks disagree with that relationship).