I agree, to a certain extent.
The kerambit is a simple weapon; the folding versions add a new level of complexity as do normal folders vs. fixed blades. I've seen the Silat guys fall to the MMA guys within their own realm of limited rules fighting. However, in the 'real world' when weapons come out, IMO this is where these guys and the Kali guys (for example) will really excel.
The Strider Tarani is a good example. I mean Tarani is a reputable martial artist and no doubt the kerambit is every bit as lethal in his hands as it appears. Heck, I think Ernie did a good demo on his site. Kerambit is for specific uses, granted... like everything else there are better tools for better purposes. For infighting, however, I think kerambits excel vs. a fixed blade of similar length. Just IMO!
Balisong are more fancy. I kind of liken them to Aikido. If you really train and understand it's limitations, it can be very effective. If not, you are in trouble. I have no doubt that the Philipino knife fighters... bantangueros? really can do bad things with the balisong. FMA has great techniques, the fact that a bali can be used as a fistpack or kuboton style instrument makes it versatile. The design is such that the lockup is much more sturdy than virtually any other folding knife I can think of, even a liner lock. They balance very, very well in the hand also. Speed of deployment is what will get you burned, especially in light of the KISS stuff. Get sloppy and you might only make that mistake once.
I, for one, wouldn't feel comfortable carrying either a bali or kerambit as a SD weapon as I have no real training with either. Doubtless, however, if you have good training, either weapon can be very effective.
Other than the ring, which can be used as leverage while pinching, for retention, or as a type of brass knuckle, I don't think there is very much advantage a kerambit has over a different style of fixed blade. In fact, one could argue that it's shape can make it less effective.
Either way, I had never seen a video of a kerambit in action, thought it would be good to share.
Here is the fixed-blade Strider version for those who are interested. Awesome piece of work.