Many people don't know the legal definition of "domestic partnership". This means that when one member of a same-sex couple goes into hospital, their partner may not be allowed in to see them, to hold their hand, to know every decision made about their treatment, to influence those decisions, because the hospitals don't know what it means to be a "domestic partner". However you feel about same-sex coupling, I think few people would consider that God would support marriage being defined as only between a man and a woman if it meant that people could not care for their loved ones in what might be their final hours of need. Same-sex marriage isn't about the "sex" part. It's about people who care about each other having the right to support each other in this crazy mixed-up world, and everybody being able to recognise that. It's not enough to wait until people understand the concept of domestic partnership. People go into hospital every day. Couples need protection now.
I'm personally terrified of this happening to me. If I had a same-sex partner in hospital and I wasn't allowed to see them, or give directions as to their treatment, when I knew it was me they wanted to make the decisions, me they wanted by their side, I'd go spare. Illness amongst family members is horrible enough as it is without adding yet more stress to people. Allow same-sex partners the chance to live, and sometimes, sadly, die, in dignity.
That's the reason I think Prop 8 is a big deal. Everything else... yes, it's discriminatory, but what really makes the case for me is the real difference it makes in people's personal lives. If you can't vote no on Prop 8, please donate something to the No On Prop 8 campaign if you live in the US. Even if it's just ten dollars, I don't care; unless you're so broke you can't afford to eat (yep, I know that's some of you, and you're excused), you can do a little something to make the lives of a lot of people easier. Advertising is really making a difference in this campaign; the no vote previously had the lead, but an advertising blitz by the Yes side has threatened that. If you care about marriage... no, even if you don't give a stuff about marriage, but if you care about people not suffering more than they have to during the worst times of their lives... it really is important to support the advertising initiative, even if just a little. I have. And with that I guilt-trip you, because I think you should put the guilt you feel to use if you're able to.
Fun fact, also: apparently if Prop 8 is passed, the status of heterosexual marriages will become questionable. I don't know too much about this, but apparently it's something like... the state currently has equal-rights laws that say that things like marriage must be accessible to everyone. If marriage between same-sex couples is simultaneously outlawed, this will create a contradiction wherein marriage itself, because it isn't equal rights, is not supported under California law. I really need some more clarification on how this works, but it's definitely an interesting factoid. The sacrament of marriage that many religious people value so much could be being threatened in its entirety by Prop 8.
[EDIT: luinied commented with some information I didn't know: Florida and Arizona are experiencing similar difficulties this election. As he said, "California's been getting more attention because it did recently permit same-sex marriage (and because it's California, and people are always paying attention to California), but defeating the other amendments is important, too."]
And yes, you may link this around. In fact, please do.