... Perhaps on no other subject have Christians more often taken the Pharisees of the gospels as a model. For example, recognizing the spirit of Christ, some have allowed for separation in cases like child molestation or spousal abuse. But to keep the letter of the law, they have forbid official divorce or remarriage after divorce.
Certainly as Christians we have to believe in miracles and the possibility of restoration. We believe an offender can be redeemed and that the offended should forgive. The Christian virtues of patience and hope are commendable. But Jesus also bids us to be "wise as serpents" (Matt. 10:16). Abused spouses can forgive their former abusers from afar, without putting themselves in harm's way again.
Is the institution of marriage an end-in-itself? Perhaps to some extent it is. The institution of marriage probably does provide stability to most societies on some level, and it surely did in the biblical worlds. However, we should be careful to recognize that it has done so in different ways at different times and places. So biblical marriages range from polygamous arrangements to perhaps arranged marriages within one's extended family.  We do not find the small nuclear family as the norm in Bible times.
But the spirit of Jesus far more bids us look at people as what need to be protected, not laws about marriage. People are the ones who are at the table--husbands, wives, and children--not legalities and ideas. To put a wife or husband in an eternal limbo of separation because of a rule, when wisdom says healing best will take place by moving on, seems completely out of sync with the way Jesus thought, especially in the age of the nuclear family. 
I remember a well intentioned believer once telling me that a person remained married in God's eyes to whomever you first had sex with. I have even heard someone wonder if a divorced and remarried couple should divorce their second spouses so they can get back with their first partner, believing that the first partner remained eternally the one to whom they are married in God's eyes. This is an extreme example of an idea driving a rule rather than love of neighbor driving our action. And it is thoroughly unbiblical.
Deuteronomy 24 actually prohibited an Israelite man from remarrying an earlier wife if she had later remarried someone else. It is true that two people having sex become one flesh, but this is true of the polygamist in the Old Testament and the prostitute in 1 Corinthians 6. Certainly Paul wouldn't have urged the Corinthians to marry the prostitute, nor would he have urged someone to wait for the prostitute to become available for marriage if she was someone's first. This perspective breaks down into absurdities upon even a little reflection.
The whole line of thinking also treats sex in a way that the Bible never does. The Old Testament, for example, is much more practical. In Exodus 22:16-17, whether a man marries an unpromised virgin he has slept with depends on what her father wants. Polygamy is an assumed practice in the Old Testament (e.g., Deut. 21:15-16), and Jacob became "one flesh" with both his wives and both his concubines. In Hosea 1:2, God seems to command Hosea to marry a prostitute to make a point.
The bottom line is that sex is something distinct from marriage in the Bible. The ideal is certainly that sex and marriage go together neatly. This is God's ideal. But having sex does not mean two people have become married in God's eyes or that they must certainly get married--a potential recipe for disaster. Those who marry only because of a rule are prime candidates for later divorce. There is an ideal, but it is not an exceptionless one.
If Christians have often been legalistic on the front end of getting a divorce, they have also been legalistic on the back end, after a person has been divorced. Perhaps a person can remarry if they were the "innocent party." Or perhaps they have to wait until their former spouse remarries before he or she can. Can divorced individuals be ministers or does a previous divorce forever preclude a person from becoming a minister? In some contexts, divorce is a kind of unpardonable sin from which one can never escape the "legal" consequences.
There would seem to be serious theological problems with this perspective. Is there any sin for which Christ's death does not atone? Absolutely not. True, we often have to live with the consequences of our sins. It takes time for communities and individuals to rebuild trust, even if they are willing to forgive. Healing can take time, and surely it does not glorify God to be naive.
But consequences should ultimately be a matter of the real world, not of artificially imposed rules. If I lose an arm doing something foolish, the laws of nature force me to live with the consequences of my actions. It is something quite different for us to insist a person remain unmarried forever after a divorce when nothing precludes the possibility of going on to have another chance at a healthy marriage. Remaining single then becomes an eternal punishment for a past sin, something quite different from a natural consequence.
It seems that this view involves an inferior sense of Christ's atonement. Perhaps his death can forgive the personal guilt of the sin but it can't forgive the social guilt. And it can't restore. We may talk about God restoring the virginity of a girl who has sex before marriage, but we don't believe it can restore a divorced person to a pure state. This perspective seems deeply problematic...
 "Endogamous" marriage where one tends to marry "within" the larger extended family to keep possessions in the group. See Malina ***. Family is not a matter of a husband, wife, and kids (nuclear family) but includes grandparents, cousins, aunts, and uncles.
 In other words, there are some significant differences between family then and now. A wife can get a job and there are safety networks to take care of children. The extended family is now divided into relatively independent nuclear families, all of whom are expected to take care of themselves. We do not live in an "honor-shame" culture, where divorce brings debilitating dishonor to the members of a family unit.