There's very little risk of any significant radiation getting to the west coast but we shouldn't assume everyone buying it is planning to eat it now. Potassium Iodide is a great thing to have in your survival kit, and a lot of people in California have ones for Earthquakes, with a huge Earthquake ripping up Japan its logical for Californians to be checking up their own Earthquake survival kits and under the circumstance adding Potassium Iodide to them. Emergencies agencies have always advocated having a stockpile of it in such kits. It obviously shouldn't be taken unless the situation warrants it but to assume everyone is getting it so they can swallow it as soon as they get it is probably a bad idea.