Andrew Sullivan links to a poll showing that Americans who personally know somebody who's gay are more likely to support legalized gay marriage. His conclusion:
If gays are really serious about marriage rights, they need to accelerate the process of coming out. It's not often that a minority group has this option - African-Americans don't. But gays, like Jews, can "pass", and by passing, we don't even give many people the option of changing their minds and hearts by better understanding who we are, and why our relationships and families strengthen society rather than weakening it.
Yes, donate and campaign and blog. But for all of those of you out there who are gay and do none of this, one simple political act can do much more: let your family, friends and co-workers know who you are. If you don't, please quit complaining about your lack of civil rights.
Hmm. I see a serious causation/correlation problem here. I suspect the linkage between knowing somebody who's gay and supporting gay marriage is not a simple case of A causes B, but a third factor causing both. Gays are probably more likely to come out if they live somewhere that's fairly liberal -- that is, the kind of place that would be more likely to support gay marriage (say, New York City). They are probably less likely to come out if they live somewhere that's conservative (say, Smalltown, Arkansas.) So people in New York are more pro-gay marriage because they're more liberal, and more likely to know gays because they're more liberal.
Now, I do think there's something to the power of coming out. (See Dick Cheney's support for gay marriage, something I have difficulty imagining if he didn't have a gay child.) But I doubt that knowing somebody who's openly gay is really the only determining factor in public support for gay marriage.