Need help/answers regarding the new Yahoo Beta mail.?

If I understand correctly everyone will be changed to the new Yahoo Beta. When reading thru the terms ( which I feel many do not do ) ,I read the following "your use of Yahoo! Messenger and all Yahoo! Messenger services will be subject to the TOS and laws applicable to the Applicable Yahoo! Company in Section 10. By using the Services, you consent to allow Yahoo!’s automated systems to scan and yze all incoming and outgoing communications content sent and received from your account (such as Mail and Messenger content including instant messages and SMS messages) including those stored in your account to, without limitation, provide personally relevant product features and content, to match and serve targeted advertising and for spam and malware detection and abuse protection. " If I am reading this correctly it means Yahoo has the right to read our mail and IM's. I certainly do not want anyone having access to my personal information. Is this legal ?? I have used Yahoo many years and do not want to change. I wonder if these are the terms with other mail providers. This invasion of privacy is to collect information to be sent to advertisers and also to guard against wrongful use of Yahoo. Am I reading the terms correctly ? Can someone please explain them more clearly ? Also, is this change to Beta a choice or requirement ?