http://www.reuters.com/article/2015/05/27/us-yahoo-email-classaction-idUSKBN0OC22F20150527 So does this suggest that a class comprising only non-Gmail subscribers could be certified against Google? Edit: It's all about Rule 23: numerosity, commonality, typicality and adequate representation. In a joint class, Gmail and non-Gmail subscribers aren't typical of each other. Gmail subscribers arguably agreed to spying, whereas non-Gmail subscribers clearly did not.