DH SPOILERS BELOW!
Do we still need these?
I'm not sure how much help that this will be to you, but Cyns brought up a good points about entering marriage under the Imperius Curse or under the influence of a Love Potion.
Didn't Tom Riddle Senior leave Merope Gaunt because he was intoxicated at the time of marriage (i.e. had been slipped a Love Potion)? I think that that would indicate the marriage did crumble through all wizarding relationships, though I agree with Cyns. The wizarding world does seem a lttle behind on most things, so I think their views on divorce and marriage would be slightly behind as well.
And didn't Remus consider leaving Tonks and Teddy? I don't have the book on me right now, but I think that he had definately considered it.
Just my two knuts, though.