What's a Kiss Between 'Friends'?

There's nothing odd about a passionate smooch when you're in a relationship - but what about when you're just friends?

That's the lip-smacking question being debated around the country's water-coolers after The New York Post published photos of Jennifer Aniston (search) and Matt LeBlanc (search) - both happily married to others - in a steamy lip-lock outside a Los Angeles eatery.

Should Brad Pitt (search) head for divorce court? Should Matt's wife move out? Absolutely not, say relationship experts, who believe that the “Friends” (search) stars, like lots of people, were caught in an unusual moment.

“It was the manifestation of separation anxiety,” said Robert Butterworth, a clinical psychologist in Los Angeles. “With the show ending next month, they are like a family breaking up after years and years of wonderful times. ...When you're going to miss someone after being with them for so long, a kiss can be like a last embrace.”

But just because Jen and Matt got carried away doesn't mean what they did is right for everybody.

“It really depends on the friendship,” said Hilka Klinkenberg, director of Etiquette International, a New York firm specializing in etiquette.

In creative industries like entertainment and fashion, she points out, people are more open to bold displays of affection.

“The atmosphere there is probably looser than if you're in investment banking,” she said. But even in those fields, a kiss isn't always welcome.

Just ask Charles Youssef, a 22-year-old Manhattan fashion designer. “I had one friend who did that to me and it was just kind of awkward,” he said. “It seemed like it would be really sweet, but it was just awkward, the whole saliva thing. It was just gross.”

Reacting to The Post's photos, most people interviewed said they prefer a cheek kiss to a full lip smack.

“Kissing on the lips is a sign of familiarity which I reserve for my girlfriend,” says Russ Bird, 28, who works in advertising in New York City.

Ava Cadell, a romance counselor and author of “12 Steps to Everlasting Love,” said most friends should be able to experience such intimate moments without having to worry about going over the line.

“It doesn't mean they are going to be unfaithful,” Cadell said. “Remember, it can happen to anybody in any situation. People don't realize how strong chemistry is - and sex is the second basic instinct after human survival.”