] In fact, it's even more insidious. A man could be sued for Breach of Promise...should he attempt to withdraw from an engagement....

Very true. I've got a slightly out of period magazine which has a section of advice on matters of the heart. It recommends the following to a young jilted woman re: Breach of Promise. (Trying desperately to make this JA-related. Right....if Willoughby had proposed to Marianne and then later recanted, and told her that he was engaged to another when really he wasn't, this is the advice she would have been given on how to encourage him to return her letters and love tokens.)

Imagine me looking up in the air and whistling while trying to look innocent and hoping that fooled Caroline.

Here's the advice:

We fear you have been duped by a man of unmeaning attentions. We are of your opinion, that he is not engaged, but told you so, as an excuse for jilting you. If, in the forty-eight letters you have received from him, he proposed marriage, you might sue him for breach of promise; but, unless he is a man of fortune, we hardly recommend this proceding, as it might occasion you more irritation and trouble, than compensation , for all you have endured. However, you might threaten him with an action, in the event of him not returning your portrait and your letters.

The same tome does point out that Breach of Promise is sometimes a viable option. The following advice is aimed more at a man who has complained that his jilted lover will not return his portrait, letters and gifts:

The lady is not obliged to return the portrait, letters, gifts, &t, supposing the gentlmean has, without sufficient cause, broken off his engagement with her. By so doing, he has treated her very ill, and she may keep all his souvenirs to bring them into court. On the strength of faithless lover's letters, very heavy damages are often awarded to the plaintiff.