As you might have read, Call of Duty: Black Ops not only rewards XP in multiplayer, it also rewards CP ("CoD points"). CP is your main currency for unlocking gear and content. Everything in multiplayer costs CP to unlock -- killstreaks, new guns, even layers and symbols that can be used to create your own emblem and logo. So CP, while plentiful (especially when you're good), is important. Losing it in wager matches puts you further away from getting whatever items or unlocks you want.
Wager Matches are a special gametype in which you actually "bet" CP on your performance. Every player that enters a Wager Match antes up a certain amount of CP (it was around a hundred in the matches I played, though if enough players chose a menu option to "double down," it got doubled for the match). With that total, you're basically betting that you'll come in the top three of that match. If you finish in the top three players, you get more than you anted, and if you're not in the top three ("Out of the Money," the game calls it), you lose your ante.
That means that if you're not good, you can lose CP quickly. "One in the Chamber" gives everyone one bullet, and while you can earn another bullet with each kill, a miss leaves you stuck with the knife. Most players would simply fire off a bullet as they ran at each other, and then knife fight to the death if they missed. I sat firmly "In the Money" during these matches -- as a pretty good pistol shot and an even better backstabber, I always had a few spare bullets to fire.
"Sticks and Stones" was probably the wildest mode. Each player gets an explosive bolt crossbow (that can "stick" explosives to other players, attach them to the wall for area damage, or kill with a headshot if you aim it right) as a main weapon and a tomahawk as a throwable weapon. Unfortunately, I suffered from a little lag while playing this one, so I never did land the tomahawk quite right. I was told that if your tomahawk finds its target dead-on, that player will become bankrupted and get sent to the bottom of the match list. The unusual weaponry made this mode feel the least like any Call of Duty game so far.
Finally, "Sharp Shooter" was the match type I enjoyed most. It offers every player the same weapon (on a random cycle that changes every minute or so), and when you make a kill you receive a random perk for that time period. It wasn't as wacky as the crossbow matches, but it was exciting as we shifted between machine guns, shotguns, sniper rifles and rocket launchers, with players falling out of and rising into "the money." The fact that I was fighting for "money" definitely, erm, upped the ante, so to speak.
With tougher opponents, I would probably have actually lost CP (and thus progress) during every single one of my matches, and I don't think that would have been nearly as fun. More casual players will probably avoid the Wager Match modes in favor of more traditional fare. In the regular modes, you can simply earn CP without betting it, and there are also individual bets on yourself called "contracts," which challenge you to complete a certain task in a certain time limit. Players who are good and willing to prove it with a gamble will probably really enjoy Black Ops' Wager Matches. But I have a feeling that, as with most gambling affairs, the rich will get richer, and the poor will just get angry.