The term "OB markers" was first used in 1991 by the then-Minister for Information and the Arts George Yeo to describe the boundaries of acceptable political discourse.
[3] An additional complication is introduced by the fact that OB markers may shift depending on the political climate, so a topic that was previously permissible may be banned in the future, and vice versa.
[4] Straits Times editor-in-chief Cheong Yip Seng found OB markers "bewildering", stating that topics deemed off-limits during his tenure included stories about a stamp dealer, carpet auctions, monosodium glutamate, feng shui and unflattering pictures of politicians.
The lack of clear definition of OB marker resulted in mixed responses by the police and the government during the "White Elephant" incidents at Buangkok MRT station in 2005.
Although the person was later let off with a stern warning,[8] Deputy Prime Minister Wong Kan Seng commented that "we cannot apply the law to some and turn a blind eye to others.
"[9] Later, a group of students from Raffles Girls' School were preparing to sell T-shirts bearing the phrase "Save the White Elephants" to raise fund for a charity.
[13] The Southeast Asian Press Alliance has described the OB marker system as "a suffocating environment where the limits of one's freedom to express is defined by citizens themselves.