President Obama's support of same-sex marriage, which he expressed last week after years of "evolving" on the issue, illustrates an accelerating pace of social change. The kind of gradual shifts that took decades or longer for other movements to achieve seem to happen faster in an era of instant communication and universal information.

In the past decade, millions of Americans changed from opposing to supporting full marriage rights for two men or two women. About 47 percent of U.S. adults favor allowing same-sex marriage, compared with 43 percent who oppose it, according to the Pew Research Center. In addition, gay men and lesbians serve openly in the military, adopt children and marry legally in six states (New York, California, Massachusetts, New Hampshire, Vermont and Iowa).

Many students wonder what all the fuss was about. Younger Americans have firmly supported same-sex marriage for some time, polls show. Obama told ABC News that blocking marriages by same-sex couples "doesn't make sense" to his daughters, 13-year-old Malia and 10-year-old Sasha.

But just because the president backs same-sex marriage doesn't mean more states will allow it, as shown last week a day before he spoke. North Carolina voters passed a state constitutional amendment banning it, the 31st such measure nationwide. Nearly every time the question is on a ballot, voters reject it. Maryland and Minnesota are among states likely to vote on constitutional bans this year. Forty-two states prohibit same-sex marriage, some via legislative action, and their laws may be hard to change. Mitt Romney, the Republican candidate who'll be nominated to run against Obama this year, opposes same-sex marriage.

Backer says: "This is about our lives. This is about our families. This is about whether or not we’re hurt by policy made in the public arena." -- Rachel Maddow, MSNBC public affairs program host

Critic says: "Proponents of same-sex marriage have created a myth of inevitability. The only poll that counts is the voters. And if you look at that, we’ve won every single one." -- Brian Brown, president of the National Organization for Marriage

Writer says: "We’ve had these successive movements of social change from African-Americans, then feminism and now gay rights. Each one seems to happen faster than the last and you wonder what’s going on there. I do wonder if in a more (Internet-)connected society, people are more comfortable with change." -- Jonathan Rauch, scholar, author and magazine writer