Marriage is tough. Trust me I know. Tough enough that seemingly two decent reasonable people can ruin each other's lives.
Tough enough that if you add some spice to it, such as inability to control your self (infidelity or anger), you can wreak havoc on it.
Take this first couple:
http://www.msnbc.msn.com/id/25839910/
They look like they will be happy a long time! Wedding night brawl. Three days later, honeymoon throwdown. Hey you never know, maybe they will have a long, loving, and very violent marriage. Perhaps they should invent a couples prison, so they can live happily ever after.

Or these folks above. Boy oh boy. And can you believe all these stories are from one weekend?

You know it is a good thing to fight in marriage, so long as you do it peacefully(ie no violence), resolve why you fought, and make up.
As they say "What doesn't kill you makes you stronger"
In these peoples cases, lets hope they don't kill each other.