Fights aren't duels. Knife fights don't look like 2 guys with a bowie in one hand and a lantern in the other, circling around eachother with 15 feet of space between them. Long blades have their advantages, but karambits are definitely effective in close quarters.
Some karambits are single edged, and some are double. There are also 3 ways to hold the karambit. If you hold it in a reverse grip, you can swing the karambit out, making it extended (looks like a push dagger, of sorts at that point.) Or you can hold it in a forward grip with your pinky finger through the ring. From these positions you can slash and thrust. Also, you can chop with it while it is held in reverse grip. And there's a lot more moves you can do with the karambit.
I got a video in a trade from forumite Randal16-1. The video is by Steve Tarani (collaborated with Strider Knives to make a karambit), and it is called Karambit: Operation and Personal Safety. Definitely, get this video. I don't know what else to say abotu it except that it should answer all of your questions.
Karambits do take training to be effective with them, though. Someone with no training would probably do better in a nasty situation witha simple drip point knife than a karambit. But with training, a karambit is very effective. Of course, this point isn't all that exciting anyways. If anyone carries anything for self protection, they ought to be training with it.
