Not so long ago, lost-love genealogy was a daunting endurance test.

To find a high school squeeze, the intrepid had to query friends, call past workplaces, scan alumni newsletters and, as a last resort, hope the ex-flame would surface at reunions.

But now you can excavate an old love in a respectable way in seconds: "friend" them on Facebook.

Mark Laaser, an Eden Prairie therapist who specializes in infidelity and sex addiction, says Facebook has become a popular venue to rekindle a dormant love connection -- especially as, more and more, it's become the domain of Generations X and Y and baby boomers.

"Like LinkedIn, it has the credibility of being a professional and social networking site," Laaser says. "It's a less obvious and blatant hunting ground for ex-lovers than"

So your lost love can initiate the contact, as they typically do, with an innocuous, ostensibly casual, just-wanted-to-catch up post. But Laaser says motives often aren't innocent: "The population that I deal with is mainly doing it for the sexual buzz, the neurochemistry, the excitement of the pursuit," he says. "Either that, or they have unresolved issues with the relationship."

And, of course, in a reality that's virtual, your exes can posture as ever dashing, carefree and sexy -- even as they click the keys unshaven in expandable pants, amid a pile of laundry and a pile of bills. (Word of caution: If most days you are in XL yoga pants with dirty hair, avoid the video approach of Skype.)

Nancy Kalish has made a career of analyzing why we seek out past romances, and what happens when we do. A developmental psychology professor at California State University in Sacramento, she wrote "Lost & Found Lovers: Facts and Fantasies of Rekindled Romances" and has surveyed hundreds of couples who have reconnected.

Most, she says, live to regret it. But nostalgic lovers, even those in happy marriages, often override their cautionary instincts, she says, because they've never completely gotten over the excitement of that high-voltage high school love.

There even is some neuroscience evidence, she says, to suggest that those raging youthful hormones can be stored as sensory and emotional memories and, literally, be reawakened. Immersed again in this infatuation, suddenly all bets (and the fat pants) are off -- and there's a visceral transformation: You feel just like the short-skirted, confident, size-5, man-slaying cheerleader you were in high school.

With a maturity level to match.

"All those old feelings and thoughts come back, and so does adolescent thinking," Kalish says. "They regress emotionally and cognitively, too."

And because the culture has changed drastically, if the flirtation progresses to a face-to-face affair, infidelity is easier, can last longer and be more lethal to marriages.

Most of our Midwestern grandparents wouldn't have dreamed of lunching with opposite-gender friends after they married. Now couples not only have many platonic friends, but boys' and girls' nights out as well as weekend getaways. So it's easy to say you're on a golf vacation with the boys or a shopping overnight with the girls when, in fact, the conduct may not be innocent.

More technology that can facilitate cheating? Cell phones. You can text or e-mail a lover right under your husband's or wife's nose -- on the guise that it's work-related -- leaving no tracks of infidelity on the family computer. Suspicious spouses tend to not check iPhones as much as iMacs; nor is it as easy to get your hands on them.

So if you're tempted to reconnect because reconnection is instantaneous and offers what seems like a harmless thrill, think again about your motives: You probably have all the friends, on Facebook and otherwise, that you need.

And, assuming your marriage is solvent and dear to you, either ignore a new "friend" notification or accept the face from the past and post a benign, polite message, says Jack Quesnell, relationship therapist for the Midwest Center for Personal and Family Development in Minneapolis.

Then run like the wind.

If the person keeps writing back and you feel you must answer, Quesnell recommends the classic, tried-and-true technique to ward off unwanted advances: Write on their wall about your significant other, in proud and loving terms.

Next: Exit out of Facebook, pronto.

Quesnell warns not to be vulnerable to flattery, idealistic memories or that sizzling chemistry. "It was very exciting back then, but it's totally unrealistic now," he cautions.

"That was a simpler romance in a simpler time of life, without the responsibilities of children, careers and mortgages -- all the things that, in fact, do test a marriage.

"As often as not, people who engage in extramarital affairs have screws missing," Quesnell says. "They wreck lives and can't, at the time, imagine all the pain they'll inflict -- usually to many, many more people than they imagine."

Kate McCarthy is a freelance writer who lives in Minneapolis.