Blah was Coke Studio's word for filtering words that could be offensive to others, to protect identity (phone numbers, credit card numbers, and other personal information.). However, this system was not 100% effective, as ways of getting past the sensor where found. (Such as putting spaces in between letters of an offensive word).
Similar Systems[]
Other games have used simular systems to "blah". Jagex LTD. used to use the word "Cabbage" for their game, Runescape. Also, the same system was used on Habbo, with the word "Bobba". The systems on both sites where removed with similar reasons of "being confusing" and 'only if some of the word was caught as offensive (often by bug), the whole word would be blocked out'. Unlike these examples, CokeStudios kept the "blah" until the end.