Anyone who's done any dating knows that there are people on the market who have the ethics of wolverines. And may not kiss as well.

But even for those who try to conduct themselves with some degree of integrity, the mating landscape is a tar pit of social and ethical ooze. It's sticky. It's uncomfortably warm. It's really, really hard to get out of upholstery.

Consider this question raised in a conversation with friends: When is the right time to inform someone you've just met that he or she should not waste time impressing you?

The single life would be so much easier if everyone in a relationship could be marked in some highly visible way. Married people are made to wear metal collars, though they wear them on their fingers, where the band is less likely to cause fainting when the wearer experiences middle-age spread.

But people in relationships that are monogamous by choice rather than by threat of lawsuit have no way of signaling that status to potential admirers in the partner's absence.

This is awkward.

I'll illustrate my point with a couple of scenarios.

No. 1: Tim has been seeing his girlfriend for a little over a year. She is out of town for the weekend at a meter-maid convention (she works for an elastic-rain-hat manufacturer). Tim is attending the 30th birthday party of his friend, Zeebort, a graduate student from an obscure island country in the North Sea, where he finds himself chatting with Wanda, a dog masseuse.

(She massages dogs. She's not a dog herself. She's pretty attractive, once you get past the mastiff hairs in her socks.)

WANDA: Oh my God, isn't this shrimp dip amazing?

TIM: I have a girlfriend.

Now, Tim has committed a gaffe here, because he actually made the shrimp dip.

Also, he has spilled the girlfriend beans waaaaay too early. Wanda has shown no sign of even being attracted to Tim, and may have been making conversation only to avoid Zeebort, who doesn't brush after consuming lutefisk.

No. 2: Mordred and Claire have been dating for about three weeks. He is dropping her off at her apartment after a Young Anarchists golf outing, and they end up steaming up the windows a bit in his car, if you take my meaning.

(Where you take it I don't care, but for heaven's sake don't let it drive.)

MORDRED: Oh Claire, from the moment I met you I sensed that you were unique. Your beauty enchants me. I've never felt this way before.

CLAIRE: You kiss like my boyfriend.

Wow! Claire let that go just a little too long.

So, the ideal time to gently apprise a person chatting you up -- who may or may not truly be chatting you up, depending on the robustness of your ego and the number of beers you have both consumed -- is somewhere between "hello" and installment-plan jewelry.

Like THAT's easy.

Not even to mention the complication of people who lie about having a boy/girlfriend. After all, it is an ironclad way to rebuff someone you wouldn't have dinner with if it were the only way to postpone your execution.

Even if you are in a relationship, and you just want to gently warn a person who seems to be on the edge of flirting with you, the mention of your significant other always seems contrived.

No. 3: Scott and Zelda have met at a gourmet-coffee bank fundraiser and have been chatting for about 10 minutes. Scott knows people Zelda went to school with, and Zelda is starting to toss her hair and put her hand on Scott's arm when she's talking.

ZELDA: … and after about an hour, we gave up and went home because there was nowhere to park!

SCOTT: Ha ha! I KNOW. It's crazy. My girlfriend also owns a car.

Ten out of 10 for ethics, Scott, but the conversation has just hit a brick wall, killing all aboard.

Nothing to do now but limp over toward the hors d'oeuvres. Have you tried the middle-age spread?