What's happened to marriage?

It's been a really tough and strange year around here.  We've been hearing a lot about people divorcing and lots of infidelity within marriages.  I believe the economy has done in a few of those marriages but the latest is a couple we know through some friends and the story goes, she found out that he's been cheating on her and not just recently but pretty much throughout their whole marriage which I believe spans at least 15 years.

Not to mention the damage it does to the relationship itself but just the sheer health risks involved when you mess around outside your marriage.  We're not talking about just one woman but  multiple women and ones you pay money for as well.  It's so sad and disgusting the lack of respect we as a society seem to have for the sanctity of marriage anymore.  We all I think, hide what's really going on behind those closed doors every day and night.  What seems to be a perfect union is anything but; however you should finish one chapter before beginning another.  What would you do if you knew about one party cheating; do you tell the other?  Are you obligated in some ways to notify the other?  It's not a huge surprise apparently that this particular husband was cheating and has cheated but no one said anything to her...  I would hope that someone would give me a bit of a heads up; but then the argument goes that she probably had a clue about it.  I am aware of one other situation for another couple that has occurred but I didn't say anything either...it's a hard decision to make.  To stir the pot or not... or is ignorance bliss?...

I have no reason to not trust my spouse but am I just fooling myself too?  I'm a consummate believer that just when things seem to be going so perfect; the rug gets pulled right out from under you!  That's my pessimistic side coming out.  It seems to not be that big of a deal around here to go outside your marriage to take care of what's lacking.  I think my views are pretty old fashion some would say but I don't think I could live with the shame or look at my children in the eyes if I did anything like that but that's just my thinking.  

The stakes are too high and is it really worth it?  It makes you reevaluate your own marriage and ask is it strong enough?