For years, Hollywood publicists have guarded the secrets of their clients' sexuality, for fear it would kill them at the box office. Famously closeted stars included Rock Hudson, Merv Griffin and Paul Lynde. Many of today's stars -- Jodie Foster, Michelle Rodriguez and Clay Aiken, for example -- have been the subject of speculation on their sexual orientation.
Though some groups may threaten to boycott advertisers, "Anyone who has a problem with it will no doubt find themselves in an increasingly bitter minority," Musto said.
"There are moments in the history of any movement when the corner is turned," Geoff Kors, executive director of Equality California, a gay rights group, told the Washington Post. "This is it. This is the tipping point."
Ted Casablanca, a columnist for E! Online and a gay man who just "married" his partner in a civil union ceremony in Hawaii, agrees that public perception of same-sex couples goes up a "notch" when stars are legally able to marry.
"Wherever the notch is to legalize in society, it doesn't matter," Casablanca said. "It's one more notch and the more notches you get, we're a part of a culture that is less inflammatory and incendiary."
Though gay marriage will make no difference for DeGeneres' strong fan base, it could have a more shocking impact on those who are still in the closet, he said.
"If Tom Cruise said, 'Guess what? After all these years, I decided to be gay and get married,' that's hugely different," Casablanca said. DeGeneres and Takei are "the types of stars who can afford to do whatever they want with their reputation.
"For Ellen, it's not a risk of alienating her fan base," he said. "She's already so family-oriented and not a sexy, slinky broad out there. She's very domesticated and secure.
"These people have already made up their minds that she is one of them," he said. "She'll say, 'You're not going to believe what Portia did emptying the dishwasher last night.'"
That conventional tone is one of the reasons Casablanca has -- so far -- not thought about legally marrying his partner, though he admits he might consider it for financial reasons so the couple can file jointly on their taxes.
"I never wanted to get married, like my parents bickering all those years or like Britney," he said. "Our very nature [as gay men] used to be bucking the system. That's how we were raised."
Indeed, in the eyes of some, these stars and their home state have already "bucked the system," according to Gary Schneeberger, vice president of media and public relations for Focus on the Family, who said his organization would not boycott actors in same-sex marriages.
"The triviality of TV ratings isn't the issue here," Schneeberger told ABCNews.com. "What's important is that the institution of marriage is under attack -- and the attackers are a judiciary that thinks its job is to make laws, rather than merely interpret them."