One might even be lead to believe that sites which tout their “deep understanding” of human motivations ought to be able to offer a degree of certainty regarding submitted information for even unverifed participants. (I suspect only okcupid would be willing to place a number on the subject’s truthfulness at the current time.)

To run with your example a little more, would I self-bond against lying about my relationship status or achievements in order to attract women? Such self-bonding would only work if it were hard to lie about having done it, perhaps the bonding agency would design a hard-to-counterfit certificate. But as long as few people were doing this, no women would ever demand to see the certificate. Making a point to show it to women at some point in a courtship wouldn’t work well, because it would either show too much interest too early or be a pointless complication once things were proceeding along nicely. If it were something I reserved for when my honesty is questioned, it would likely in practice be less effective than an eloquent verbal reassurance, or some more direct demonstration that what I had said was true. Announcing the bond to my entire extended social circle, regardless of romantic interest, would probably be the best of a set of bad options, but it wouldn’t help with women I’ve just met, and wouldn’t be especially useful, because social networks already have informal mechanisms for punishing liars.

In short, I don’t think you can reduce the reasons for not doing this to simple issues of “weirdness.”

There are lies that are easily and soundly disproved being spread constantly, lies that do a great deal of damage to all of society. “Death panels”, for one. Not only are these not punished, in certain places people are rewarded (financially, politically, and socially) for how well they can spout outlandish lies that significantly damage the majority of the population (Glen Beck comes to mind).

I don’t want the government mandating The Truth either, but when a lie is damaging, provable, obvious, and constantly repeated… doesn’t society have a vested interest in stopping it?

The law does not recognize voluntary exchanges of gifts or “services” in romantic relationships as “damages.” If it did, pretty much everyone could file a lawsuit for their time and money immediately following a breakup. This would be nightmarish, because no one can be trusted and there’s almost never clear hard evidence. And proving the actual value of damages is nigh impossible.

More generally, proving that someone is lying and then proving that this lie caused damages is generally far more expensive than the lie itself. Moreover, in many cases, allowing people to sue or prosecute on such grounds would net a whole lot of innocent people being sued by the greedy or malicious, which is not a desirable outcome. If lies were easily detectable or provable, the legal system could effectively discourage them, but it probably wouldn’t even need to.

On the bond bit: if I’m an honest person, I’ll pay out of the bond if you catch me lying, so I probably won’t lie. If I’m a dishonest person, I’m not going to admit that I lied, so you’d have to sue me, which could be quite difficult, and you’d have to have a lot of money at stake to make it worth having a lawyer. It’s not a huge help reputationally, since the former could see a lot of frivolous lawsuits and the latter could see a lot of legitimate ones, and an outside observer would have great difficulty telling the difference. In other words, if people put up bonds about their honesty, you could trust people you think are honest, and you couldn’t trust people you think are dishonest. This is not much of a step forward.

For example, consider the case where a married man lies about whether he is married when trying to attract a single woman into a relationship. Single women typically insist they do not want such lies, and it would be easy to determine if the man is in fact married. So why do we not use the legal system to discourage such lies?

Such lies did in fact incur a variety of civil and criminal liabilities in the past, both under traditional common law and various statues, until roughly two generations ago. Wrongful seduction and breach of marriage promise used to be uncontroversial common law torts, and many common law jurisdictions also had the crime of seduction (with varying definitions) on their books. As recently as 1938, Frank Sinatra was famously arrested in New Jersey for criminal seduction of a woman of good repute. If I remember correctly, the charges were changed to adultery and then dropped when it turned out that she was in fact married. (I don’t know if this means that the local authorities had less of a problem with adultery than deceitful seduction of an unmarried girl, but in any case, the latter was a criminal offense.)

All these laws were gradually abandoned in practice and abolished during the 20th century. For reasons that would be interesting to discuss, but alas too complicated for a blog comment, our civilization has gradually drifted towards the present strong ideological consensus that the government has no rightful authority to regulate or arbitrate non-commercial consensual sexual acts between persons above the legal age of consent, and the legal trends have followed these broader social ones. Thus, I’d say that this area is rather special because of its ideological weight, and not a good source of examples for your general points about legal toleration of lies.