I think the danger posed by heavy metals is more worrying, but yeah, the quality of sushi and sashimi isn't what it was back in say, the 70s. At least with parasites you can kill them with acids and heat. I've seen enough horrible news related to both categories of risk to know that I no longer include it in my diet. I only eat seafood when I know where it came from, and even then I rule out some sources.
Mercury, cadmium, arsenic, PCBs, plastics.... screw that, I'll get my omega 3s and 6s elsewhere thanks.