http://www.pcworld.com/article/115692/article.html
EDIT: Quote > But Google is planning to scan e-mail and add advertisements that it thinks are relevant to the messages. Additionally, the Gmail privacy policy warns that messages, even if "deleted" by a user, may still be stored in the system, even long after users have closed their account--something that some privacy campaigners believe may be in conflict with U.S. and European data protection and privacy laws.
Article about privacy right there. I talk with people and they always say Google was forced into reviling they read people's gmail. Wasn't true.