Though many companies are pulling their ads in response to the "voices of the people", Korean government regulators are looking to address the legalities involved. Although one ISP blocked access to boycotters' posts, that doesn't appear to be the direction of their inquiries.
Hi-tech Korea is one of the most connected countries in the world, so the response was lightning-quick: people began turning themselves in to the Justice Ministry and the prosecutor's office, according to a story at Korea Herald: Hundreds admit to pushing boycott; the Korea Times adds another vector to the protests:
The boycott is now moving in a new direction; netizens are promoting companies who gave up putting advertisements in the three. Samyang, food manufacturer, recently benefited from the boom, as many people are promoting the company's food rather than Nongshim, who refused to withdraw the ads.
This depth of feeling is something Americans haven't been able to muster regarding the Iraq War--either for or against. Korea's more or less with us on the war, having just activated a replacement unit of 300 troops in May, but are diametrically opposed when it comes to beef over 30 months old.
It is amazing to watch the Lee government basically be caught by surprise at every turn, and backtrack and apologize. While it is true that you can't run a country by responding to every whim and wind-change, a well-stated apology from a certain current US President would go a long way with me.