Why keeping e-mail private is that important?

E-mail is very important asset. It is used everywhere, from social networking to bank account. In most cases people have one e-mail address which is shared with all services they use. It may have bad consequences...

First: in event of data leak/security breach criminals can easily locate all your accounts and use this information in malicious way. Second: e-mail is used to track your activity and also to profile you. By using random aliases trackers are unable to perform their job efficently. Third: random aliases prevent phishing attacks. When you generate an unique alias which is used by you at only one service - you can be sure that no one else can send legitimate e-mail to the alias.