Around March 2015, AdMob will begin supporting inventory for a new standard sensitive ad category, Social Casino Games, as part of a limited beta program.
"Social Casino Games" are defined as simulated gambling games (including, without limitation, poker, slots, bingo, lotteries, sports betting, betting on races, as well as other card games and casino games) where there is no opportunity to win anything of value (such as money or prizes).
Standard sensitive categories are allowed by default. Learn how to opt-out of this sensitive category.