Arguing that marriage will be devalued if gay people are allowed to marry, is like arguing that the £20 that I have in my purse will be worth less than £20 if you have £20 in your purse too.
I don't believe that divorce is easy. I do think that it is very sad, and I think a some people use it as an easy way out. However, thank god that we can have divorce so that women don't have to stay in abusive marriages because they have no other choice. I overheard a women trying on her wedding dress at the same time as me - she said "oh well, if this marriage doesn't work out, i'll wear the other one next time" - she was serious
I think that some people tend not to think about marriage as a long term commitment, but rather as a big party for a day, and forget about the actual act of commiting yourself to another person everyday for the rest of your life. Marriage something you do, not something you have - but I've said this before.
It seems to me that most of society is instant gratification - "take away", "fast food", immediate, now, buy now and don't pay for six months, buy one get one free, instant gratification, instant credit, mobile phones, text messaging, internet, interactive tv etc etc. (not that all of this is bad, just reflective of where we are at). Therefore, I feel that marraige is sometimes viewed this way - and thrown away if it doesn't instantly provide what we want.
And lastly, I believe that if a child is secure and loved, whether inside or outside a marriage, then that is the best we can do. They are no formulas and can't be studied as such - there are too many variables. My cousin came from a loving family home where his parents were childhood sweethearts, and the dad went out to work and came home at 4 pm everyday, and the mother stayed home, and he went to private catholic school etc etc. He's in jail for double homicide. Sometimes, stuff just happens which can't be blamed on anyone else.