It is ironic that extramarital affairs are so much more condemned in recent years, when marriage is being attacked on ever other front. (Divorce, gay marriage, etc.) In the past, it was generally accepted, although frowned upon, that some men would have extra marital affairs, especially when in positions of power. (I got the idea for this post during the Petraus scandal, but didn't get a chance to flesh it out until now.)
In the past, many presidents, generals and other people in powerful positions had affairs. While these weren't usually public, they weren't as secret as you would expect, and those who knew just accepted that as part of life. Certain needs had to be met, and if one's wife wasn't meeting those needs, someone else would. There was no big scandal to it, and no one "went to the media" with that info. If they had, it wouldn't have been printed anyway. Sure, a certain population of the general public wouldn't understand, but it seems to have just been rationalized as part of life, by those who knew.
Back when divorce was a very rare and difficult process, men stayed married even if there were “issues,” instead finding a mistress, and this was the "acceptable" solution. Now that divorce is easier, and happening all the time, that is the socially "acceptable" solution. Interestingly this causes extramarital affairs to become a much bigger deal than they used to be. It would appear that the general public isn't nearly as offended by a public figure abandoning his responsibility to his wife, as long as he is open about it and gets a divorce. If he tries to get the best of both worlds, and maintain his marriage, while secretly sleeping with someone else, well that is a national scandal. Fifty years ago, a public figure getting a divorce would have been the big scandal.
I am not saying that one approach is better than the other, they are both wrong. I just think it is interesting that while morals seem to be declining in our society in every possible measure, extra-marital affairs happen to be becoming much less socially acceptable than they were 50-100 years ago. That is an interesting illustration of how our culture now views marriage. Most secular perspectives see it as unnecessary and quaint, but they do recognize that its only real value comes from actually honoring the commitment.
As for my perspective, while I can imagine how the scenario comes about, I can't imagine having an affair. Now I am not even married yet, but certain things in life aren't going to change. My reasoning is simple, and maybe even selfish from a certain perspective: "relationships are way too much work." Having an affair is, in effect, developing another relationship. That takes work in itself, plus I am not stupid enough to think that it won't eventually have a negative effect on my existing relationship, which was undoubtedly a lot of work to develop in the first place. So the whole problem with having an affair is that it’s just too much work, besides the obvious moral implications. Other people, to whom relationships come much more naturally, won't see it as much as work, and therefore be more tempted. But if I am not going around developing sexual relationships with women to "get my needs met" when I am single, I am sure as hell not going to be doing that once I am married.