IMO the problem with weight loss supplements or rather the way they are marketed is in the implied results and moreso the dynamics in which they can affect you.
Most are marketed that they work by "burning fat", i know in a vague sense this is what happens in the process i.e. fat burning hormones penertrate the fat cell freeing it up for energy etc etc, but really, can 3 pills a day enchance this process THAT much as a stand alone? IMO, no.
And this is where a lot of supplements sporting these claims become unstuck.
Realisitcally a over the counter thermogenic fat burner is going to raise your metabolic rate by a minimal amount.
Take a 'fat loss aid' supplement and combine it with a clean diet and a good cardio/resistance routine and BAM, you have true fat burning.
I said fat loss aid instead of fat burner because thats where i believe the true gold nuggets are in this market, those supplements which can help add a piece of your missing puzzle.
Case in point, i dont mind eating clean, i dont mind the intense cardio or the longer period cardio and i certainly dont mind hitting the iron, what lets me down is my appetite and the sheer amount i can and often will eat! It doesnt matter if ive been restricting my kcals for 8 weeks, i can resort back to eating 5k cals in a sitting with no adjustment time needed. So for me, my "aid" would be a supplement that can add the missing piece of my own personal puzzle - appetite supression.