I really don't know about that one. The Internet has been cited as one of the driving forces behind the growth. The real marital growth area, according to One Plus One, is in divorced people giving marriage another shot with a new partner. Zo and Norman are a case in point again - he has been married before. People expect great things from marriage, and if they don't get it, they look for something better.
People are clearly committed to marriage.
There was a nice piece in the paper last week, in which one chap said 'I really believe in marriage, I do it every eight years'. People want to get into relationships where there is a sense of emotional and legal security. But it is not necessarily for life. What you are seeing now is serial monogamy. Marriage isn't necessarily the permanent state that we commit to verbally when we get married.