Yeah that is true. I tried Yo once and that was enough. Aside from that Yo place I always stay away from any 'fast food' sushi or sashimi. For raw stuff, I do try to eat at more reputable places. I figure it might be safer. But who really knows.
Depends really on where you are, all cheap Sushi places i have been to in Europe were absolutely horrible, some use frozen fish, it tastes like shit.
In Japan, there are several cheap Sushi chain restaurants, they are better than most expensive places in Europe. But once in a while i also go to an expensive Sushi place here, and then it's really out of this world.