When I buy a linerlock folder and upon inspection see that the lock barely engages the tang or if it exhibits blade wobble even after adjusting the tension on the pivot, I'll send it back. Personally, I'd prefer a lock that's a bit harder to unlock and a blade that's not centered when closed over a sloppy linerlock that may disengage when slight pressure is applied, but I can understand why you would expect a bit more attention to detail on more expensive folders.
Consider how fast the lock will wear on a folder. I've had a few high-end production folders with linerlocks that have worn rather quickly (some more than others), not enough to interfere with routine stuff like pealing fruit, opening envelopes and such, but not suitable for their so called "tactical" use. Then again, others I've used have performed admirably and can still be found in my EDC rotation.
My idea of hard use is cutting through several piles of cardboard boxes, skinning large game, light chopping, heavy rope cutting or any task that requires you to apply heavy pressure to accomplish the cut. If I don't think a folder will cut it, I'll use a fixed blade instead. Again, most of my linerlock and framelock folders have worked as advertised from day one. Spyderco, Benchmade, Al Mar, Microtech, Kershaw, CRKT and Outdoor Edge are a few name brands I own whose linerlocks have never failed on me. A few from other brands have been sent back for minor QC issues, but the problems have always been fixed. Of course, some models are designed for harder use than others, but I've used them confidently enough and none have accidentally closed on me.
I do refuse to buy linerlocks from Böker and Schrade. They make decent slip joint folders and fixed blades, but I've yet to see one of their linerlocks that will give me enough confidence to use it for anything other than opening letters.