Originally Posted by
AUDirt
Let me summarize for you:
1) The airline will (most likely) cancel your itinerary as soon as you skip one of your segments. So don't try it unless you're on your way home.
2) It's against the airline's rules.
3) The airline probably won't do anything to you, particularly if you only do it once or twice.
4) A group of FlyerTalk readers will organize a mob and try to hunt you down. A second group of FlyerTalk readers will come to your defense and a great battle will ensue. (Think "Braveheart" but with Roll-aboards instead of horses, laptops instead of swords, and "Diamond Medallion" hats instead of helmets

)
This is much better advice... it is against the rules, and the airline could probably come after you based on the CoC (though there are very few occurrences of this happening and it's usually the biggest fish). The biggest thing is to be aware of the itinerary cancellation, so be sure not to foul that up.