Anecdotal evidence is not evidence.
And it is more about how the state shouldn't have the right to change the definition of Marriage, which is a religious construct that predates government, not how it affects Hugo the Canadian.
The effects will be the same as the widespread of remarriage and contraception. People will see Marriage as less important, more malleable and get divorced with more ease and it will be seen as the norm. Other deviant sexual groups will seek "Marriage equality", like polygamous, and incestuous people.
In the US, we do all have the same rights. I never understood that argument. Homosexuals have the exact same rights as everyone else. They want us to change an institution that many of us hold as sacred, and integral to our nation's family structure.
Edit: Marriage did not start out as a property thing. There was Marriage before the idea of private property even existed. Regardless, it existed way before governments, so governments have no business in the thing.
(I can already see it coming "I refuse to talk to you, you're only 18, you just don't understand, blah blah blah")