Beach, according to a Glenn Matthew, who claims to be in a same sex relationship he experienced problems with Centrelink. Glenn claim when filling in an online Centrelink form he encountered problems. Possibly if what Glenn said is true, it may explain why as you put it
"Gays have been less than keen to register their 'love' with Centrelink," maybe they can't.

http://forums.whirlpool.net.au/archive/1859392

I can not substantiate what Glenn Matthew posted, no more than I can substantiate what you claim as being true.

"I was in a sandwich shop the other day ordering a sandwich.

The man next to me was ordering one I particularly didn't care for.

Although what he has chosen has absolutely no effect on me, my life or the enjoyment of my own sandwich I think it's my right to deny him his own choice".

No the sky hasn't fallen in but as I've pointed out society is always less "equal" after progressive reform, what's now written in stone is that there's no such thing as "marriage equality". Gay men seem to divorce at half the average rate and Lesbians at double the rate of all other pairings, when you take into account physical gender differences we now have three distinct types of marriage, not one.
Expect to see different traditions and ceremonies arise for the two new types of marriage, for example it's common for one party in a Lesbian marriage to appear in drag at the wedding ceremony and one gets the impression that this is done with all the usual solemnity of one so betrothed, it's not comparable to say, getting married in your bathers or using a Kenworth prime mover as the bridal car.
I don't like the word irony but the big mistake made by the pro side was the use of the term "Marriage Equality", most reasonable people are of the opinion that we can accept different strokes for different folks and that point of view has been vindicated, what we've got is greater diversity in marriage, which is the exact opposite of "equality".

Aside from the marriage argument, I have a question that goes beyond that.
If a pair of married homosexual men applied to adopt a young boy and
if you were the public servant charged with giving approval would you
be happy considering the risk of having that child come back in 20+
years and charge you with incompetence or worse for what happened to him ?

Dear Bazz,

I imagine that adoption agencies would have to
apply the same strict criteria to all couples wanting
to adopt. Be they straight or gay. All couples
should be investigated for their suitability
to be parents. Because as we know the mistreatment
of youngsters can apply to all sorts of people.

Child abuse, involving such acts as burning children
with cigarettes, locking them up in closets, tying
them up for hours or days, not feeding them, or
breaking their bones - is alarmingly common, and
probably causes many of the thousands of runaways
that happen each year.

Foxy that is about the weakest reply I have ever seen you post !

If I was the public servant, I would refuse to be party to it and pass it to my boss.