Given by the name,
Risk is a game of uncertainty and you know you're liable for disaster. What you didn't expect from the game's namesake is the risk of hating everyone around you by the end of the game. From personal experiences I have gleaned but one simple truth about
Risk: by the end (if you even get to the end of the game) there will be blood. Never in my experience has a game ended in anything other than a major bought of shouting, and some severely bruised egos. Alliance's will be formed and then completely shattered leaving boyfriends and girlfriends pissed at one another, and best friends as ballistic enemies. Winners will be handed their asses to them by a person who buys a devastating card. Players will bitch when it's not their turn and become severely ADD. Oftentimes assorted detritus is thrown at the board in frustration or apathy, causing pieces to fly off the board.
Namaste mother f'ers!Another probable cause with Risk frustration is the massive amount of rules to remember. Often times you should get cards or extra people in certain circumstances that are really easy to pass over. However, there's always that one guy that remembers all of the rules conveniently on his own turn. It's really easy to manipulate the game with newb players by not fully explaining the special rules.
Speaking from experience the most frustrating part of Risk is when you just can not roll above a two. This fact let's you get three pieces annihilated by one defender. It's probably the worst feeling of defeat in any game, ever.
The big however, HOWEVER, is that Risk is the most incredibly addicting party game known to man. There's something about the board game that just keeps you coming. Maybe the pieces are secretly coated in crack, or military strategy games are really that addicting (take Chess for example). I think the brute force of the game is what keeps you needing to try again. When you see the map monopolized by your pieces, there's a rush of ecstasy. This also explains why you feel as if you've had a swift kick to the balls when your entire territory is taken by the underdog. So no matter how consistently nasty and rude we are to one another by the end of the game, we simply can't stop having Risk nights. Perhaps we're just board game fetishists or perhaps there's something deeper here. Either we're eerily screwed up or the makers of Risk just really have it all figured out. Maybe they understand our deep psychological need to be repeatedly slapped in the face, as long as there's the promise of glorious victory.
So in conclusion, Risk is a game of theoretical and very actual warfare. My advice to you is to...

In Which You Risk Life, Limb, and the Overall Happiness of All in the Room