Starsan starts to loose it's effectiveness when the pH gets above 3.0. Since wort/beer pH is higher than 3.0, and since it is only a residual amount of Starsan solution mixed in with the wort/beer it is rendered ineffective.
If you were to pitch your yeast into a concentrated Starsan solution, then they would most likely die. But I'd like to believe those bastards put up a good fight first.
Primary 1: Apfelwine
Primary 2: Buddy's Brown Porter
Primary 3: "Brown" Hefeweizen (oops?)
Primary 4: Chocolate Stout