Valve intentionally leaked a trailer for Left 4 Dead 2 in 2009 because the ESRB would not allow its release due to content restrictions on violence and gore, according to former Valve writer Chet Faliszek.

This revelation sheds light on the historical challenges game developers faced with content rating boards and the creative strategies employed to navigate these regulations, particularly concerning marketing materials.
Valve intentionally orchestrated the leak of a trailer for Left 4 Dead 2 in 2009 because the Entertainment Software Rating Board (ESRB) would not approve its release due to content restrictions. Former Valve writer Chet Faliszek revealed this in a recent video, explaining that the ESRB's guidelines prohibited trailers featuring "graphic and/or excessive depictions" of violence, weapons, blood, gore, or offensive language.
At the time, publishers needed ESRB approval to sell games in major retail stores. Valve had prior experience with the ESRB's stringent enforcement, having previously altered a promotional image for Left 4 Dead 2 that featured a hand with three gnawed-off fingers. The ESRB had also requested the removal of trailers for other games, such as D3's Dark Sector and 2K's The Darkness, citing similar concerns about excessive violence and content likely to cause serious offense.