Since I saw that documentary about synthetic THC, my confidence has decreased a bit and if the weed now tastes or feels a bit strange, the thought of synthetic THC comes to mind. Unfortunately, I can imagine that there are shops that sell laced weed. That is why I only shop in well-known shops with good reviews and I am generally very confident that I am buying good stuff.
But, even with quite a few good reviews, a shop sometimes disappoints. For example, I recently bought four strains and three of them (silver haze, amnesia & jack herer) were all equally nasty in taste and effect. I vape weed and really like the taste of it, but these buds were so gross it made me feel sick. The fourth kind was their 'own weed' and even though it still tasted a bit ok, I had so little confidence that I just threw everything away. First and last time for this shop. I still remember being happily high that night and thinking of giving that newly bought Amnesia a try. I immediately regretted that because I went to bed with a headache. Really to get sick of.
Unfortunately I don't know what synthetic tastes like and therefore I don't know if and with what these buds were laced, or were they just poorly grown or not cured (properly), or a combination of all of that; I have no idea... but in over twenty years of almost daily-tasting weed I have never bought & experienced such bad stuff.
In my early years of weed I noticed some grinding between my teeth and then you know there's sand in there to weigh down the buds, but even that tasted better. By the way, I have only been able to buy that sand in one shop in all those years. So all in all I am very happy with my purchases & the Dutch shops.