Actually, the reverse is true. People are saying not to go to Jpn or S. Korea because they watch a bit of news and suddenly they 'think' they are an expert on radiation. In fact, these are most likely the same people who ran screaming into the supermarkets grabbing all the salt they can get.

Speaking of radiation knowledge, no one is absolutely certain that it's exceedingly hazardous or acceptably risky to travel to the affected areas. I guess the best way is, let people make their own choices.

After all, it's their hard-earned money (and life) they are spending for the travel, not yours 

Well, wanted to go japan this May but decided to skip it not because of the radiation/earthquake but because I'm worried about the infrastructure (whether the trains will be running and if the attractions are opened).