Some good insights in the above posts!
I've had pocketknives fall out of my pockets more often than I can count. One thing I did that kept me from EVER losing my Scout knife while in Boy Scouts was to take a long shoelace and loop it through the bail/lanyard loop on the knife, tying the ends together. Thus, I had maybe a two-foot lanyard on my knife. I would then run my knife through one of the front belt-loops on my pants, and then back through the loop, which had the effect of tying the knife to my belt-loop with about a two-foot length of strong string attaching it there. Not a tough knot to undo, but that long length of string meant that I could use the knife for almost any purpose without untying it. If I dropped it (only ever happened when it was closed), it would end up hanging in the air somewhere below my knee. To stow it, I'd just roll the knife up in the shoelace and drop it into my pocket. A little odd, but I never lost a knife that way.
I think that a key aspect of any knife is to be able to test that individual knife rather strenuously before relying on it for survival purposes. That puts a premium on unconditional warranties such as what Himalayan Imports offers, and (maybe) Busse, Ranger, and Swamp Rat. (Any others? Correct me if I misstated on any of the above names.) With Himalayan Imports (the only brand from the above that I've owned), I always take each new knife out into the yard, and, at a minimum, chop it forcefully into a heavy log and tug on it side to side. The goal is to see if it's going to snap off under heavy use. I have NEVER had any Himalayan Imports blade fail under such testing. Note that there are an awful lot of good-reputation knives out there that you don't DARE test that hard, just because if they actually DO fail, you're probably going to be out the $50 . . . $100 . . . $150 . . . whatever you paid for the knife. Me, I'd be a lot more confident going out into the woods or desert with a $65 Himalayan Imports khukuri that I KNOW can handle being forcefully leaned-on by a 180-pound man, than with a $100 knife that I've never tested because I know I'd be sitting there with only a $100 pair of scrap-metal pieces if it broke. I wonder: how many guys who carry Ontario Bagwell 400-series-stainless Bowie knives, or Cold Steel Trailmasters or Laredo Bowies, or even Becker knives, have actually subjected them to heavy testing before adopting them for carry for potential "depend-on-it-for-your-life" applications? Might you not be better off with an Ontario Old Hickory butcher knife that you have actually determined will throw you back across the room if you clamp it into a vise and lunge against the handle, than with a $150 blade that you've never even used to chop a 2 x 4 because you can't afford to chip the blade of such an investment?
The one knife I've had catastrophically fail was an Ontario FF6--a vaguely small-Bowie-like knife with an 8" blade. I was doing light snap-cuts against a soft-wood pole when the tang snapped about 2/3 of the way into the handle, and the pommel went flying off into the night. The inch-wide blade narrows abruptly to 1/2 inch wide where the ricasso meets the tang, and continues at about 1/2 inch until it is again abruptly narrowed to about 1/4 inch for the last couple of inches of the tang. That 1/4-inch section is threaded, and holds the pommel on by being screwed into it. (The pommel is a roughly-mushroom-shaped piece of steel, the stem of which fits into the Kraton handle material; there's a threaded hole in the stem which accepts the threaded 1/4-inch end section of the tang.) Obviously, a lot of force in any blow is going to be concentrated on that 1/4-inch-wide piece of threaded tang, with a lot of leverage right where the tang enters the pommel--and that's where it broke. The blade itself didn't wind up flying away--though, with the pommel gone, it would have come out after not much more use. By way of full disclosure, I had removed some Kraton from the sides of the handle in order to make it more grippable (even my large hands have trouble getting a really, really good grip around the round, baseball-bat-like handles of some knives.) I didn't return the knife to Ontario, because (1) I think the problem is a design problem, and I just don't trust any knife built as that one was built, so I don't want a replacement; and (2) actually, the way it broke, there is still enough 1/2-inch-wide tang that I have plans of someday just making another handle that works with the tang, and put the blade back into use.