Hey, if you lost a knife or two I'm sorry. I sympathize. But in no way do I agree that clips are bad or useless. Today I carried a Vapor and a Mini-Griptilian, and both stayed safely in my pockets (front right and back right, respectively). Some knives' clips are tighter and stronger than others, but in general they tend to work rather well for me.
Funny story:
Some clip designs are better than others. The clip on the Spyderco Walker Linerlock is terribly loose -- the only one of my knives that is so. I lost it once into the crevice of a chair in our office at work. The chairs got moved over time, and I had not thought to check in them anyway. By the time it was suggested, it was months later and the chairs I checked could not be assured to have been the ones that had been around at the time.
Over 2 years went by...
I finally decided to go to Knifecenter.com and get myself a new Walker Linerlock. THE DAY AFTER I ORDERED, my manager, who had known about the loss of the knife, called me into an adjoining room on our floor. He told me to dig down into a particular chair, between the back and the seat. There, covered in two years' worth of dust, was my knife. IT HAD SAT THERE TWO YEARS UNDETECTED UNTIL THE DAY AFTER I ORDERED ITS REPLACEMENT. Talk about weird coincidences.
I sold the replacement that came a week later to my brother. I think he has since lost it, but I'm not sure.
---Jeffrey