Flash memory has a limited number of write cycles. In a recent question, @Rsya Studios discussed problems with reads affecting neighboring bits, which is correctable up to a point. Neither of these problems is like a switch; there is some period where performance is marginal.
Back in the days of floppy drives, there was a method of copy protection called "weak bits". Marginal bits were purposely written to the disk, which required special equipment. The bits could not be duplicated by copying the disk on your home computer. These were tested by doing multiple reads. If the results did not come back the same every time, the disk was recognized as original.
Does anyone know if a similar technique has been applied to testing flash drives for imminent failure–looking for marginal bits through multiple reads? (I'm not talking about writing marginal bits or writing bits and seeing whether they are marginal; just reading existing bits to see if any are marginal.)
Edit: This question is about a testing method and its efficacy for flash drives. Please focus on that and refrain from discussion of whether it is worth testing flash drives or whether flash drives should be used at all for one purpose or another.