In strike-prone South Korea noisy street protests by angry workers are a common sight. But there was something unusual about one such gathering outside the headquarters of LG Telecom earlier this year.

Instead of disgruntled employees demanding higher pay, the demonstrators included several of the country's most famous pop stars, such as Um Jung-hwa and Kang Ta. It was the equivalent of seeing Britney Spears and Justin Timberlake manning a picket line.